1. open the DG Archive and look at some of the setups in there. mostly, we have had pretty balanced setups in the past.
2. this topic from mafiascum can be extremely helpful, if only for Xylthixlm's posts. he is an extremely experienced mafia game designer and runs the automatic mafia irc. i wish i had this thread when i first started.
http://www.mafiascum.net/forum/viewtopic.php?t=12906
3. find a co-moderator who would be willing to listen to your unique ideas and help you balance the game. i would recommend Xiivi or Marshy, or both. stress to them that while you want their help balancing the game, you have a lot of unique ideas that you want to find a way to include.
all three of these steps are equally important and you should be sure to do all three :]