1. Make sure your bike is in good shape. You'll need good brakes, good tires, and the bike has to hold your load securely. Make sure you can repair flats.
2. If there's a bear box, use it. Use bug spray when you stop. Don't feed the animals.
3. Be mentally prepared. You'll run into horrible headwinds, and long days, that you have to be able to deal with.
4. Most of the route is on lightly traveled roads without shoulders. Get comfortable with taking the lane and riding with traffic.
5. Water can be an issue. Especially on hot days, drink early and often. If the maps say "no services next X miles" take extra, either in extra bottles or a bladder (or two).
6. Eat enough salt and other food to keep you going. I have trouble sweating salt out, and then trying to eat enough to replenish it without making myself sick.
7. After a few days or weeks, you develop a sense of what feels right. If a situation feels wrong, do something about it -- either get out of there or get help.