If hanging pictures, I have used regular picture hanging hooks, but instead of just pounding them in, pre-drill a hole at the correct angle for the nail slightly smaller than the nail, this way you won't crack the plaster in the surrounding area. As for hanging shleves, try to find the studs in the wall and again, pre-drill your screw holes and then mount. If screwing into studs is not an option, use toggle bolts. I have tried almost every fastener on the market, and the good old toggle bolt is still probably the best bet for that situation. Any further questions, feel free to email me.