You don't need formal teaching to be good, I've seen way too many people self taught that are simply amazing. What helps me, when I draw something, is to reference the pose from an actual/person or picture.
Not a bad start though! The only way to get better is practice!
I've never had an art class. Unfortunately, my website is currently down. Here's some suggestions for a basic beginner, however:
"How to Draw Comics the Marvel Way" This inexpensive book is an excellent resource and, to me, a must have. I've seen this book on the shelves of professionals who work in the RPG industry (miniature company concept artists as well as the people who draw such pretty pictures in those massively expensive books). It's got a great, basic explantion on bits such as perspective, height, and movement.
Get a *GOOD* book on anatomy. Not a skinbook, but a book for artists that shows bone structure, muscle structure and placement, movement range, and angles. "Anatomy for the Artist" (I can't recall the author and it's still packed" is one of the many that I have.
"How to Draw Cutting Edge Comics" and some of the others from this series are really good.
And lastly, practice practice practice. Find an artist who's work you like (online, comic books, whatever) and just copy their work. As long as you don't try and sell it, you'll be okay. Then post your work and ask for CONSTRUCTIVE criticism. Also check out sites specifically for and by artists (like Deviant Art) for posting your work and getting feedback from people other than us. :-)
Seriously, I started drawing people when I was in high school and don't practice enough with paper these days to keep up my skills. They will get rusty after a while. I, more or less, paint minis these days, but have been recently inspired by people here to try and pull out my pastels and penciles, if I can find them.
I also use magazines for reference, from Vogue (wonderously inexpensive) to National Geographic (horrifically so) to Rolling Stone and movie mags. Sketching your favorite actor/actress/rock star can be a lot of fun.
Worry about shading and whatnot after you have the basics down. Once you have perspective, you can worry about the shading later.
"If I fail, they write me off as another statistic. If I succeed, they pay me a million bucks to fly out to Hollywood and fart." --- George A. Romero
"If I had any dignity, that would have been humiliating" --- Adam Savage
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Only formal class I've had isn't a drawing class, it's like a painting and arts and crafts thing, and I was terrible at it. x.x
But anyway, ya don't need formal classes. I've improved mostly from looking at others artwork, practicing a ton, a couple books, a couple tutorials, and critiques.
Just keep drawing. 
Sometimes what can be as helpful as a teacher is just someone to discuss things with. The artists on this forum are really open and helpful, I find, if you approach them in a respectful and sincere manner.
I also learn about twelve new things everytime I ink the work of someone who's better than me. A lot of art is shapes and representation of shapes, whether they're literal or abstract. Even if you mind doesn't immediately comprehend what shapes you're inking when you do it, your hand begins to understand a little, I find.
You do have nice clean lines already. That's a gift and you should treasure it.
Being a former Art Teacher and more importantly a Huge Comics Fan, I can tell you one thing... Art Classes are for Traditional Formal Artists, your basic painters, sculptors, and in betweens.
If you want to be a Comic Book Artist, that's a whole other thing.
Granted some of the skills overlap, anatomy, perspective, design and color. But your typical art class won't be giving you any immediate satisfaction for being a comic book artist.
They will teach you other things, equally important things that if you want to be a traditional artist would be ideal. Formal training is like having a personal trainer to push you.
But many schools are low on technique and high on individual thinking and motivation. Their goal is not to make you a carbon copy of each other, but to give you the basic tools, the knowledge of those tools, and how to make yourself improve with them through personal exploration of subject matter and thinking.
Do you see how odd this would be if it were applied to a comic book artist, it would be like only giving you half of the goods.
Comic Book Art is specialized training. You HAVE to know your anatomy, that part can't be argued. You HAVE to know your perspective and design, if you're going to do full pages, tell a story AND sell your work. You could forgo the color training but you'd be missing out on a whole new aspect.
Also I'd like to stress the story telling part, great comics do that with even the smallest of expressions on the hero. Why are they smirking, why are they angry, why are they smiling. Each one of those examples is ripe to be filled with some thought balloon and or "heroic tag line". You don't have to be a great writer, but you do have to be universally understood.
If you want to draw a picture of an impaled enemy, the details you put down will tell the story for you.
Kheprera has give you some excellent beginnings, there's so much more to touch on. Materials, Movement in your figures, and I can't stress enough to know your comic history, so that A) you don't repeat what someone else has created or B) that if you do, you do it in your own original way.
An example of that might be an illustration of your character's death scene. Many comic characters have had a death scene in their run, and each one is similiar (for dramatic reasons) and different because of who the character is, what their background is and what makes them fun to read.
Look at the Death of Superman story and the make believe Death of Batman in the Dark Knight stories. You couldn't have them die in the same way, it wouldn't make sense. But a good artist will make you feel the story coming off the page.
From your drawing alone, I can tell you that the arms are the best part, your legs are off, and a little too blocky looking. Look at some leg reference in the same pose. A good example would be a sports magazine, because players are always moving in different positions.
You should be able to find a similar pose. Granted a photograph and a drawing are very different, so you will have to simplify the lines a bit to help you redraw them. By studying the lines, you will learn the form. I could go into bone structure, but that's a different lesson.
Get yourself a piece of tracing paper, a piece of carbon copy paper (this should be at any staples if they still make them), and some good white paper.
Play the carbon copy paper on the white paper, place both of them under the image you want to trace. Place the tracing paper over the image, and with a soft pencil, not a pointy one cuz you'll rip the tracing paper. With a soft pencil apply enough pressure to trace the outline of the form of the body.
If you do it right, the pressure will push down on the carbon copy paper and that will make an exact copy on the white paper. Try not to move the carbon/white paper because if you move it, and start tracing again, the last few lines you placed down, won't be where you left them on the tracing paper.
That is to say if I trace a line of a finger, then look at what I did, accidentally move the paper, then try tracing the rest of my hand, the finger could be off to the left or right, depending on how much I moved the paper.
Try tracing the entire image before you look, I know it will be tempting to look but you'll be better off waiting.
Now is this drawing, no. It's tracing... I'm getting to why I taught you this, something I also taught my 6th grade class on how to draw comics. This is to teach you line, form, structure and why an artist chooses to draw the way they do.
If you do this with a photo, you'll learn the shapes that make up the image. That is just as important as drawing freehand, and looking down occasionally on your page.
If you memorize the lines it takes to create a whole image, you'll eventually be able to apply that to your own style, your own images, your own creations, because your brain will have learned to see the shapes, and remember how to make them.
Is this cheating? Yes it is, but am I grading you, no I'm not. It is a method to make you learn faster what the shapes are. BUT, if you don't take the time to draw without using this method, if you don't apply the lines and forms you're trying to memorize, then you will be cheating yourself. You won't be drawing like you, you'll be drawing like the original artist or photographer.
This method is a practice method. You have to learn the lines, that make up an arm, over and over again, then get yourself a blank page and recreate what you remember.
Naturally this works best with photos if you want to learn more anatomy. And when you use other comics, it teaches you why those artists use the kind of thick or thin lines they do.
This method doesn't work if you don't do the other work it requires, in fact it will do more harm to your drawing skills, because you have to MIX what you remember, what you see in real life (Ie landscapes, people, animals) and the kind of style that inspires you TOGETHER.
Only then will you develop your own style.
The book Kheprera spoke of teach the same thinking, they teach you practice, application and results, but they do not teach you how to draw like you. No one can teach that, drawing is a part of everything that we take in, what we like, what we don't like, your brain will process that as what you want to capture on paper, because part of it is what excites you, what makes you happy when you create something from nothing.
Good Luck.
LJ
I wanted to stress that drawing from life can't be beat. Have someone pose for you and try to capture the pose or expression if you're drawing a face. In my art college anatomy class, we did 30 second drawings, 1 minute drawings, 5 & 10 minute drawings and the excruciating 20 minute drawing.
This was so our brains could be taught to think faster if we only had 30 seconds or 1 minute to draw. With 5 and 10 minute drawings we were told to add more details, so we had to "look" for those details. With a 20 minute piece, it is all about a finished piece of work, composition, lighting, and design, as well as detail and always anatomy, anatomy, anatomy!
SO there you have two methods to teach you different things, and similar things. Oh and don't forget to draw your same drawings over again, once you've learned or felt you have learned more, at least you will be surprised at the progress, at best you will have a drawing that is more thought out and closer to what you want the finishing style to be.
Yeah I sucked at those gesture drawings 
You know, that is actually quite good. I think you got the basic propertions right. There are some issues about leg thickness, joints etc., but the overall pose and propertions are good.
As others have said, get a good book on anatomy, and practice on reference shots. There's a girl on DeviantArt who has produced a lot of great action shots for people to use as reference.
Unfortunately I can't remember her name right now, but I will try to find it and return with it.
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Main Villain: Elenor Seahawk (Mastermind lvl 44; Necromancy/Poison)
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Fight my Brute: SMASH
Hey Lady, would Poser be a good substitute for a model? I've been using that for a few of my pics and it's been a real boon.
My husband has Poser, and it can be a very useful tool.
I always recommend to use what you're most comfortable with. For me, it's books and other comic art I can reference.
I need to see if I can get a space somewhere while I'm waiting for my website problems to clear up.
"If I fail, they write me off as another statistic. If I succeed, they pay me a million bucks to fly out to Hollywood and fart." --- George A. Romero
"If I had any dignity, that would have been humiliating" --- Adam Savage
Virtue Server: Kheprera, Malefic Elf, Lady Omen, Night Rune, La Muerte Roja, Scarab Lafayette, Serena Ravensong, Kyrse, and Arachnavoodoo among others.
I just wanted to thank everyone for their suggestions. You gave me some great ideas, and I hope they will help to better my drawing ability.
And...I kinda meant the legs to be big. 
I actually reduced them down. 
Burne Hogarth is your friend.
...I really need them.
Anyway, this is a WIP, and still needs an impaled enemy. It an action pic of my main scrapper Deadly Towers.
Deadly Towers
I've never had any formal art teachings, and this isn't done yet, so be kind.