What are the punctuation rules regarding acronyms?

Neither one is wrong. It’s a matter of style, and styling varies from publisher to publisher. Within a given document or paper or article, you should follow a single practice: if you write N.A.S.A., you should also write U.S.A. and U.K.

Most places these days do follow a style that omits the periods.

Grammatically speaking, you leave in the dots.

Well, say U.S. for example. If you take out the periods, you get US. people will think you are putting you and me.

My son went to NYU – or is it N.Y.U.? I’ve seen it written both ways. For well know acronyms, I think it is common to leave out the period, but certainly always correct to put it in.

I leave them out if the term is an acronym that is spoken as a word (such as NASCAR or SCUBA). I tend to put them in if it isn’t (such as C.I.A. or U.S.A.)

Depends on the policy of the institution. The Army (whom is world renowned for their use of acronyms) leaves all acronyms capitalized and without periods.

WTFDIM?

or should that be W.T.F.D.I.M.?