I've been the person getting the help, and I've been the person doing the helping. And I'll tell you now, they're both very good feelings.
The truth is, you don't have to do that much to help out a new player. A little kindness, such as a few answered questions or helpful tips, can prevent them from feeling overwhelmed and leaving. You'd be amazed how much it can put you at ease just to know the people around you are willing to be *polite*, let alone friendly.
While I'm bouncing around the city, I like to keep an eye out for folks who stand out to me somehow. If they have a cool name, fun outfit, or I just like the cut of their jib, I'll tell them so. If I see that they're new in town I'll ask if they might be interested in a free costume slot, and if they say yes then I'll give them what I call a "new player welcome kit": a set of event salvage, some inf to use it, and a tour to Annah to turn it in. Then, if they're not in a hurry to get back to something, I'll ask them if they have any questions. It doesn't take that long, it's a great break between missions, and I usually find that I had a good time doing it.
So, like Winter said. Next time you see someone who could use a hand, try sparing ten minutes for them. You might just like it 
Great words of truth.
@Zethustra
"Now at midnight all the agents and the superhuman crew come out
and round up everyone that knows more than they do"-Dylan
and round up everyone that knows more than they do"-Dylan
(There's a TL;DR version at the bottom)
Last night, I had about a half hour left to play before I was going to hit the sack. I did not have any desire to do anything specific, and since 30 minutes is not that much time, I resolved that I would simply chat the time away.
Then I saw a free player, whose name I had seen a few times before over the Help channel, requesting help on a mission. I figured why not, I was on my 50 Sonic/Sonic defender, I could probably offer a hand. I send him a tell, get to his mission in Peregrine Island, and I see that he is a lvl 41 StJ/WP Scrapper, fighting a radio mission featuring Arachnos at +3/x3. I think, "Okay, that's a bit much, but should be doable. I'll boost his resistances, throw Disruption Field on him, and let him go to town on the enemies while I lower their resistances with my attacks."
We start off weak. I notice his attacks are not doing a whole lot of damage, but I write it off since most of these enemies are red and purple to both of us. Then I notice his blue bar seems to be hovering on the low side, but again, I write it off as a consequence of a lengthier fight considering it is taking us a while to kill these guys. We get in trouble with a bigger mob and we both get defeated. Regrouping, we decide that I should pull. So I pull around the corner, and expect that he'll catch them as they come around, but he doesn't! I end up dog piled and defeated again. At this point, my impulse reaction is frustration and annoyance. That's when the realization occurred.
No one had ever taken the time to show this player the ropes. He had not been PL'd his entire career; I had seen his character name for a while, teamed with him on lower characters, and he is still just now reaching 41, even after 2XP weekend. Yet it was clear that no experienced player had ever taken the time to give him some advice. His low damage output was most likely due to uninformed enhancement/slot placement decisions. His rapidly depleting blue bar was probably a consequence of no one advising him to slot up Stamina. (I didn't get a look at his build, but I wouldn't be surprised if he did not have Quick Recovery.) Finally, upon asking him, I found out that though he was familiar with the "pull" strategy because he had seen it done, he did not know that, as a Scrapper, he would be expected to catch the incoming enemies before they reached the less resilient puller.
I am not saying anyone should be a martyr and dedicate all of their game time to educating the new players. All I am saying (all I CAN say for that matter) is that I am here right now because, when I first came to the game, a couple players had the patience to show me how to get the most out of my experience. This was the first MMO I had ever played, so everything was new to me, and I am sure my ignorance, my apologies for said ignorance, and constant questioning may have been grating. But they took the time. And I am frequently grateful to them for it, because had they not, I probably would have quit out of frustration and may not have come back.
TL;DR, in summary:
I cannot tell you to help inexperienced players. I cannot make you feel guilty for not helping inexperienced players. All I can do is ask that the next time you feel the impulse to ignore a player, or get frustrated with a player due similar reasons like those I have outlined above, take a second and offer some help rather than shunning them. Sure, there will always be trolls around, but most of these players have just never been told otherwise. A couple years down the road, you could be that player to whom he or she is grateful, just because you took the time to explain a couple key mechanics that would enhance their gaming experience.
@Winter. Because I'm Winter. Period.
I am a blaster first, and an alt-oholic second.