I'm not sure if I was clear, but SpaceClam had my meaning right, push it around your driveway with teh engine off. You just want to make sure it rolls straight with the rudder stick center and the trim lever centered.

That's as good as you can get. You will need to use the rudder on take offs, there are just too many transient forces. Some planes react more than others and therefore require more rudder use than others, but very few go absolutly straight all the time (I'd say "none", but who knows, there may be one out there. I've never seen it though).

After you've flown the plane, and used the trim lever on the rudder, you will want to re-adjust the rudder and nosewheel settings so you get the a centered trim lever and the plane rolls straight with the engine off, and flys straight with out having to mess with the trim lever. (At least that's what you're supposed to do).