What to use for surface rust?

I finally got the bumper sticker that the previous owner had stuck to the deck lid :angry4: and found that there is surface rust where the sticker had been. I'm not going to be able to afford a paint job for a while, but I want to stop the rust right away. What should I use to take the rust off, before I spray some primer on to stop it from coming back?

Thanks for the info!

DaveZee