I like to mix things up sometimes, giving characters roles they wouldn't normally be expected to have. For instance, making Penelo my heavily-armoured, axe-wielding tank. Though in my most recent game, I've tried to keep them on fairly distinct 'career' paths, using skills and abilities that're consistent with their storyline occupations. Vaan remains a single-sword wielder with a moderate range of magic, Balthier uses guns and crossbows and focuses on techniks instead of spells, and so forth.

Though those allocations went out the window slightly once my team literally gained more License Points than I had any use for.

While my exact team varies from time to time, it usually involves Balthier, Basch, Fran and Penelo.