Ditto the rollout... It takes just a few minutes, and it's the most accurate.

One thing I do with a new bike or new computer:

I used the GPS in my company van to measure one of my commute routes, and I noted mileage at various reference points in addition to the total.

I'll take that slip of paper with me on a commute and jot down bike comp. mileage next to the GPS numbers. Once I get home, I'll fudge the wheel diameter setting up or down a few mm to compensate. For instance, my road bike's wheel setting measured 2140mm, but it was far enough off of the GPS measurements that I had to reset it to 2150mm.

Anal retentive? You betcha. If I'm going to sweat for my miles, I want to log every d*mned inch.

One tip: Once you get the correct setting, trim and stick one of those little Brother P-Touch labels on the side of the computer body. Likewise, you can label the last known odometer reading as your zero reference... My road bike's label reads 0 = 38,463.2... Newer computers allow you to reinput your odo reading, but the early-90s Specialized SpeedZone I have doesn't.