Clowns do not get along with other clowns- they fight to the death. Maroons are supposedly the most aggressive, and Clakiis the most likely to bond with an anemone.
You can get mated pairs of clowns, and sometimes- if you're lucky, if you get 2 different sizes they will pair off- clowns are hermaphrodites and the larger will become the female. Your best bet for 2 clowns would be an already mated pair of clarkiis, since they usualy won't bother other fish unless the other fish is perceived as threatening their anemone.