I attempted them on a cake this weekend, and I kept getting the "tip" on top of the dot when I pull away the piping bag.. I hope that makes sense.. how do I make them look like perfect circles?

You need to pull your tip off to the side when finished piping the dot being careful not to lift your tip away from the dot while you do this. It takes a bit of practice. You can also touch up with a slightly dampened artists/decorators soft bristled paint brush.

damp finger works fine, also.

If it's a crusting frosting you use, just allow it to crust and gently tap the 'tails' down.