Don't bother looking for some fancy, computerized trade-in kiosk either. In most stores, trades are accepted at the customer service desk, while "select locations" have a "dedicated Trade-In desk" inside the games department. If all that human contact is a bit much, you can also trade in games online at Best Buy's pre-owned games site. Gift cards will be mailed within two weeks.
The website has a handy estimator to calculate the value of your used games. We're not quite sure what the basis is for trade-in value though, considering Alpha Protocol clocks in at $27 while Mass Effect 2 snags you just $8. If any of you out there take advantage of Best Buy's new program, be sure to let us know about the experience in the comments.