Tasha Greenbottle (aka Jenevieve DeFer) has an excellent guide to creating balanced, effective Hero System characters for any genre or campaign on her blog here, cross-posted and debated on this thread in the Hero discussion boards.

She assumes a good working knowledge of Hero, so some of the mechanics may not make much sense to a beginner, but the general principles are accessible.

It also acts as a very good guide to the sort of information a GM should be providing to players.