The best, most expensive way- have a frame expert check it and straighten whatever is needed. Racers often spend the extra cash to try to be as fast as possible after a crash.
The most common way- ride it with no hands to see if it rolls straight on a flat road, see if it feels like it corners normally for both left and right turns, check the tire wear- it is normal for the left side of the front tire to wear faster for countries where you drive on the right side of the road, because the center of the road is usually higher for rainwater runoff. Check to see if the chain sprockets are wearing the same amount on both sides.
Last edited by Jeff in Kentucky; 12-30-2010 at 03:56 PM.