Err...Have you clean up your sketches before scan them?
Sketches: I'm not really sure if it's your scanner or not. I've found that when I scan my sketches, the pencil is always very light and I have to adjust levels in photoshop to make the linework darker. This inevitably also makes unwanted marks and smudges darker, which I then have to go back and erase. So, I guess to answer your question, I edit my sketches after scanning without exception. I imagine this is all subject to personal preference.
Tablet vs. Mouse - I got my tablet about a year ago and really love using it instead of the mouse, but I wouldn't go so far as to say it's a requirement for intricate digital art. I created just as intricate pieces using my mouse as I do with my tablet. The main difference I see is that it takes me much less time to finish a piece with the tablet than with the mouse...and my hand doesn't hurt so much afterwards.
Inking - It's really personal choice. Ink and pencil both add different qualities and feelings to a piece of work. I tend to like clean bold lines that I can't achieve with a pencil because I'm not technically skilled enough to make the most of pencils, plus as I finish most of my stuff off with colours in photoshop, it just looks better inked. If you do want to ink but are afraid of messing up your sketch, I recommend trying it out digitally, but with a program that allows you to make layers. That way, if you don't like it, you can always just delete your ink layer and be done with it. Also, I've found that zooming in really helps to achieve smoother lines. It is a little awkward at first because you can't make the large stroke you normally would with a pencil or pen, but you get used to it after a while and it becomes easier with practice. When I first started, my inking was very shaky and boxy as well, but after a lot of practicing and erasing, I got much better and faster at it.
I'm not an expert by any stretch of the imagination, but I hope some of this helps a little. :P
Why do my pictures always look so dirty after I scan them? I always see these "sketches" but the area/page around them always look so clean and pure-white. Is there editing involved after scanning, so that only the lines are seen, or do these people just have really good scanners...?
My next questions is in a way tied to my problem of messy scans: How do you color thinsg like shading? I guess I could try, but look here. See how the shading is sort of complicated? Now, for someone who knows what they're doing, that would be a big deal if it were a painting or something. But lets assume this was mostly done on computer(even if it wasn't, lets just think for the sake of my question). How do you get this sort of itricacey? I'm going to get one eventually anyway, so... Are there tablets involved in doing such complex things conveintly?
I've done shading with pencil drawings before, but I've alwasy been scared of coloring them, because it might just look like a mess after the scaning and me trying to color...
And my last question: Should I ink? Sometimes I'll just darken my lines at the most, but I've never considered actually taking a pen to my pencil lines. If coloring, I'll usually just go into Paint and follow my drawing with a thick black line, but its just not the same as my own, natural hand movements(kinda' boxy, even if I go really slow).
So yeah... There're my questions, have fun...