Make sure the steering ratio is square, braking power is even, the gears shift smoothly, and the chain glides around in a smooth cycle. Also check to make sure all bolts are the right size and tightened. You should check the bushings as well. You can do so by propping the bike on its seat and then trying to rattle the wheels from side to side. You will need to hold the frame still. If you can rattle tightly bolted wheels it means that your bushings are too small. While you have your bike up side down you should check your bearings too. Just give each wheel a spin and listen for a ticking sound. If you hear ticking it means that your bearings aren't greased very well.