A good thing to do is sit down and read the game and arena portions of the manual
(It may be a bit arduous but it's necessary for good game analysis). Then do a full analysis of ways to score / prevent from scoring. Then you start putting ideas down (nothing design specific) just ways that you want your robot to play the game, anything and everything within the rules, nothing is too ridiculous (ok maybe some are but they can lead to new ideas that could be great and that's the point). Keep in mind it's all about how you want to play, not how you're going to accomplish that (that comes later). Just try to get every way you can think of to play the game out there. NO SPECIFIC DESIGNS! Can't stress that enough. You can get into specific designs once you know how you want to play the game in general.