Most of the time I cringe when a level 2 asks for 15 gold, but every once in a while, a lowbie will run up to me and actually appear to be new. Just a couple nights ago, a level 8 gnome rogue asked me for 20 silver to get some bags because he ran out of bag space. Been there, done that. Since he seemed polite and genuinely new, I gave him 20 gold instead.

I've seen low-level people with really terrible gear, we're talking level 20's with grays or whites, so I'll craft a ton of stuff and send it to them without telling them I'm doing so. I've bought BoE blues or rares off the AH for dirt-cheap, knowing they'd sell for a lot more had I not snatched them up, so I send the seller extra money and let them know it was worth more than they sold it for, so I wanted to make up for it. I help people who have trouble with killing mobs or who get bum-rushed, I help people in dungeons when they aren't sure what to do, etc. I give buffs to people as I run by them (when I remember to, anyway) Pretty much the same thing everyone else has done.
I've had random acts of kindness done unto me, too. I've had high-levels give me gold even after I tell them I have mains I can send myself money from, but they don't mind. It's always nice when people buff me, too.
Even if I end up getting walked on in the long run, the warmth I feel inside by helping people less fortunate than myself is reason enough to keep doing it.