The best tip I can give to get faster is to practice something each time you go out. Just riding aroud helps, but when you are focused on something you progress faster.
Each time you go out to ride decide on one thing to improve on. Whether it be berm corners, rutted straits, tabletop jumps or whoops, try to improve on just that for about 30 minutes, after warming up. Then take a break and do laps or play around a while. Then come back, and do another session just focusing on that one thing. Finally try to incorporate that on thing into the whole track for a while.
One thing at a time will eventually add up to a complete package. Focusing on fixing your weak points will make you a faster rider.
Finally, it a very bad idea to go ride by yourself. If you get hurt badly no one is there to get help.
If you still choose to go solo, then carrying a cell phone with you while you ride is a definite must. If you do get hurt you might, -repeat-, might be able to get help.
A riding buddy is the best, and cheapest, solution.
[This message has been edited by krash133 (edited 03-01-2001).]