I do find myself saying "no" and "don't" sometimes, but I try to teach my little ones by actions. For me, the big one is my glasses. I wear them all day, and dd used to constantly try to grab them. First of all, I don't want them broken (both dd and ds1 have broken my glasses at some point...with ds1, I was broke, and ended up without glasses for about 8 years). Second, I hate things getting into my face...fingers, toys, whatever - drives me nuts. All I did was gently peel her fingers off the frames, and say "glasses aren't for touching" (well...I did say "no" and "don't"...but usually not). Eventually, she figured out that my glasses weren't a toy. It works - it just takes a long time.
DS2 is in the catbox phase right now. We don't have anywhere around here that we can put it, so it's driving me quietly crazy. We take him out, wash his hands, and tell him that the "litter box is only for kitties". It hasn't worked yet, but it will...