If you have a spoke key (the right size for the spoke nipple you have) and the internet then providing it really is a simple truing job you'll find a thousand sources of useful information. The trouble is when a wheel goes out of true it's usually for a reason, a broken spoke for example. If you've whacked the wheel, and you know it, then it may not be a simple truing job. I've been given wheels to work on that I've been told just 'need a bit of truing' only to find it's been wrapped round a tree or run over by a truck. Contrary to popular belief wheel builders can't perform miracles, more's the pity.