Here are some more thoughts, get them jumpy, very jumpy to the point of paranoia. I like to keep armor pretty low, if the characters have big guns fine but I want them worried when they hear the first gun shot.
Also, lot's of folks talk about coercing PCs into immoral decisions but if they want to be good, that's fine, let Mr. Johnson play off that, tell them they are going after a drug lord and let them find out after they shoot him that all he did was rob Mr Johnson's corp to buy food for his kid, then Mr. Johnson tries to turn them in and the targets family put's a bounty on there heads, oh and his kid starves. Let them think they are good and find out latter they did something really bad, then keep showing them how it was even worse than they thought. But still let them be good some times, keep there hopes up.
Also, if they try the no food thing feel free to start changing there stats to reflect unhealthy starving homeless lowlifes.
Lastly, make sure they have something to lose, once in a while you can kill a character but you can always have stuff stolen, contacts lost or killed, and if it seems like there fault all the better.