Like Gnome said, all fish fight. The degree of aggression is directly proportional to the amount of alcoholic beverages the fish consumed before it left the bar....<G> Okay, that's not true, but certain species and families of fish are known to be more aggressive than others. When you find a fish you like, read about it first, and see what type of "personallity rating" it is given by the guide you are using. Mixing fish with similar "personallity ratings" usually works.
Also, all healthy fish are active fish. Any fish that is inactive is either sleeping or seriously sick. There are different degrees of "activeness" as well. Danios swim around like they're on crack, deep bodied tetras chill, cories are spaztic, and a pleco moves when a pleco damn well feels like moving.
Go to your LFS and simply watch the fish. If you get a heache watching a particular tank zip about, then those fish are not what you're looking for. If the fish put you to sleep watching them, then perhaps that's not what you want either.
There is no sure fire formulate for mixing and matching fish, everybody has their own tastes as well as fish having their own requirements. I've a friend who's got a very active tank with barbs and danios that is never still, but he's decorated it in such a way as to make their darting about fascinating. My own personal tank is a very calm tetra tank that is still and peaceful.
It is up to you. Just research the personallity of the fish you are interested in, then make informed decisions.
~~Colesea