Don't be afraid to explore new possibilities
Simple mafia mechanics can get a bit boring sometimes so it's best for you to change perspectives, make variants like the ever popular damage variant used in tDD and Rocket, or interesting concepts like S4's city capture system, or Xilia's time mechanic. Even though you might make some notorious variants like S3's tier system, it will help generate "some" interest in your games.
Limit yourself to what you can do
I know how contradicting this sounds when I just said to explore new possibilities, but hear me out. Always know when to draw the line when it comes to implementing ideas because if you fail, your ideas become counterproductive to what you are doing.
Try simpler games before diving into the complex games
Try to follow a progressive GM style, like for a beginner, do a vanilla variant, then after GMing a few games, be creative. Doing this complicated for your first game might just confuse you.
Google Docs or Excel is your best friend
Personally, I use Excel because I'm more familiar with it and makes things more private, but you can use Google Docs as well. When I was hosting S2, S3, and Fangirl, I used Notepad :P Planning S4, MCM Scratched, and this new small game I'm working on, I switched to Excel.
Finish your goddamn game
I'm looking at you Mathia, MCM, Babylon, FDL epilogue, GAU epilogue >.> If there's one thing I'm irked about, it's this. If you are doing a game, make sure you see it from conception to death.