My advise would be to take a two step approach to asking for a raise.
First, ask your boss / supervisor that you'd like to have a "performance review". This would show him / her that you're interested in knowing how well you're doing in their eyes and show that you have initiative and want to improve yourself.
In the review, ask how you are doing specifically against a) expectations, and b) other coworkers. If you rate at or above on either of those, you should be in line for a raise. But don't ask for it in this meeting.
Also ask what specific areas you could improve on.
Then take what you get back, and work on those areas for about 2 - 3 weeks.
Then ask for a second meeting. This is where you can bring up the fact that you're preforming above average, show the salary data you have (bls.gov is a good resource in the US as well) and ask for a "reasonable adjustment in salary" to "bring you more in-line with your peers and industry standards".
Note that it's a piss-poor economy, and I'd be really surprised if any company is going to be giving out much in the way of raises. I would hope for an "inflationary" raise and call that a success (2 - 4%). Then plan on hitting them up again when the economy improves.
Hope this helps