It really depends on how much you're willing to spend. The first step is to treat it with Weigle's Frame Saver. If you;re looking to repaint it, you have a lot of options out this way. Bilenky is excellent...but pricey. Tom Kellogg. Plenty of others. Powder coating might be an option as well.
Depending on the severity of the rust, one avenue is to take it off with a file and cover it in clear nail polish to protect from future rust.