I'll try to keep this short because Ken and Chris have stated most of my process.
Ken's team uses something similar to what i have been doing for about 3-4 years now with my teams. To extend Ken's line of thinking to link Chris' line, you have to go form asking WHAT are we going to do, to HOW are we going to do WHAT we said, and then ask HOW MUCH will each function/system cost and benefit WHAT we are doing? By cost I mean things like weight, time, personnel resources to design and manufacture, etc. You can also use some of these costs as a way to figure out the trade-offs between which systems you choose to build. For example, if you have 20 people on the team, and your drive system will take 3 weeks to design and build with 10 people working on it, then you have to cut back somewhere else.
My only other additional comment is let the numbers guide your decisions. Ken gave a good example of this. You can find many ways to play the game by breaking down the scoring at the beginning and trying to compare the bets points combination to the most realistic combination of systems on your robot. This doesn't mean to go conservative, but to select something that is realistic.
There are plenty of great engineering tools out there. A great source for these tools is form a company called GOAL/QPC. They produce a number of little books for under $10 that are just filled with useful tools. I would recommend the Memory Jogger II as a good place to start getting acquainted with the tools. The Teams Memory Jogger, the Creativity Tools Memory Jogger and the Project Management Memory Jogger ams also be useful depending on what your team needs are. Their website is
here. If anyone wants to know what is in these books I have or have read many of them. The books are also available on CD.
Steve