Just use some soap; mix it up in the pan before it goes down the drain and you'll be good. The amphipathic soap molecules will surround the grease and keep it from sticking to your pipes.
If you're worried about it, every few months flush the drain with some lye. Mix up a few gallons of a relatively weak solution and put it down the drain. About an hour later, flush the drain with a couple gallons of hot water (how hot you can go depends on your plumbing).
The lye basically converts any grease build up into soap, and the hot water will flush the soap away.
Alternatively, you can use a steam cleaner to flush the pipes, if you have plumbing that can take it.