I was taught that if the dent is deep or you have a crease in it, start with the outer edge of the dent and work your way around it in a circular pattern with a body working hammer or a rubber mallet and something that is close to the contour of the panel you're working. Then as you go around start closing in closer to the center, kinda like a spiral. That way you can re-stretch the metal and lessen the chance that the dent will pop back in when you touch it, since the metal is stretched inward, you have to pull it back out the same way.
I just did this to my buddies 90 Honda Accord and it turned out pretty smooth and all I did was use the round end of a small ballpeen hammer and gently worked it out. Now there is no dent, and there is also no dimples coming from the backside outward.
Just my .02
These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.