I have a rat training book, but since I've been working so much I haven't had time to really read it.
1 on 1 basis, with zero distractions in a room they're used to being in.
When ever they do something you like give them a treat (Even if it's just a little thing. Start off training with a BUNCH of treats, and gradually reduce.)
Clicker training works, too so I've heard.
I started with a clicker, but with the girls found I didn't need it. Just lots of word repetition. All my girls know the word "Up" (even Gadget, who's blind), and will stand on their hind legs to get treats.