I am making a baby shower cake for someone who is having a boy. I am thinking of doing fluffy white clouds for the border and for the top of the cake. Does anyone have any suggestions on what tip I use or any techniques?

I'd use a large-ish (maybe 5?) round tip. Practice on some wax paper until you get a look you like. Buttercream makes some pretty clouds.
HTH

Depending on the size of the cake use a #12 round tip; vary your pressure and make reversed shells

I use a large star tip and a zig zag motion .... narrow at the beginning of the cloud, making it wide in the center and then narrow at the other end.

I use those zip loc baggies and snip off a corner instead of using a tip.

For me, the baggies do the job! I do try a few clouds on wax paper first..

good luck......

I use a large round tip (I think I use a 5 too), and make small circles touching one another. I swirl the tip as I am piping. I posted my Curious George pic, dont laugh it was one of my firsts, but the way I make my clouds hasnt changed. Its in my phots if you want to look.

Thank you everybody for all of your help!! Will post a pic when I get it done!