My incredibly ancient writeup on the subject:
Its surprisingly easy! As long as you get started early, that is. When you bring home your new baby African Tiger Fish (ATF), you have to start the breaking process immediately. In order to use my method of breaking your new tigers, you need to take four simple steps: 1- Use teacher fish...
www.monsterfishkeepers.com
After I wrote that, I got to the point where I would feed them small live crickets. The movement of the crickets would get their curiosity and trigger the feeding response, and when they were consistently hitting crickets without hesitation, I'd start mixing in pellets.
Once they got habituated to hitting anything on the surface, sinking pellets or fish chunks were taken readily. Getting them off of live is the hard part, but once they're off live they turn into garbage cans.
The younger you make them transition to dead food, the easier the transition will be.