1. If I don't know you, don't try to touch my baby. Just because I occasionally look pleasant doesn't mean I won't bite you if you reach for my baby.
2. If I do know you and you would like to touch my baby, please confine yourself to playing with his feet. They are just as pudgily squeezable as his hands, and less likely to go directly into his mouth along with the germs from everyone whose hands you just shook. Stroking his punk-spiky hair is also a fun, acceptable alternative.
3. If I do let you hold my baby, don't interpret that as permission to offer him your fingers to suck. Do I know where your fingers have been? Do you even know? There's a reason I attach a pacifier to him when he gets passed around. (Exception clause: Grandparents With Clean Fingers.)
Need I add how immensely (albeit discreetly) gleeful I am when BabyGuy glurks on Scofflaw Babysnatchers?