For what it's worth, here are some "secrets" I learned in my racing and training.
* Get a plan to train. Follow the book "The Mountain Biker's Training Bible", buy a plan from Lynda W., get a coach like TJ, or whatever. Just get a plan and follow it.
* Make your plan adaptable. Family, friends, work, and flooded basements come first.
* If you have a goal event, do other races first to see what it might be like.
* During your training period, get thin. It's much easier to loose a pound off the average person's body that the average person's bike. Be kind of hungry sometimes.
* Don't push it going down hill. It's a waste of energy and potentially dangerous. Going uphill fast is how races are won.
* Train to your weaknesses. An XC mountain biker needs endurance and the ability to put out 1-5 minute all out efforts. If you have great top end speed, but poor endurance (like a sprinter), train your endurance and long intervals.
* Learn how to eat and drink on your bike. Find food and drink you like and figure out how much of it you need for a given effort. Energy drinks work fine for an hour or two. Anything longer and you'll want a gel or an energy bar. Hammer Nutrition has a very good line of products.
* Before spending a ton of money on a bike, make sure you will have enough leftover for the other stuff you need like padded shorts, water bottles, a car rack, emergency tools, etc.
* NO MATTER WHAT, keep it real and have fun!