How do I clean some paintings?

I would go to a hardware store and purchase a tack cloth. It’s a flannel cloth treated with a sticky substance to remove dust from walls that have been newly sanded, so they can be primed and painted. It’s not wet, doesn’t leave a residue, and should remove any surface dust and dirt. It’s hard to suggest anything else without knowing what they were painted with, and if there’s a varnish on them or not.

experiment on the painting of the the two people making out, not the clown! I repeat: DO NOT RUIN THE CLOWN! :D

Also, welcome to fluther, mom!

If the friend who made the paintings is reachable, I’d check with them and find out what paint s/he used. Except for watercolor on paper, you can clean any painting with soap and water, gently, gently….

It depends on the actual paint.
http://www.ehow.com/how_5079544_clean-paintings.html

Is it an oil painting? I had a beautiful oil painting that needed cleaning. I called a local art gallery, and they told me to use a damp rag with a mild detergent, Ivory dish soap. It turned out beautiful. Use very little dish soap, and don’t have the rag too wet. Good luck!