Along with proper hydration, there are some key points to focus on before slinging your leg across the seat of your dirt bike so before you go guzzle a lot of water and start pounding out laps in an attempt to hone your skills make sure you're adhering to these basics below.

The Core Basics for Motocross or Off-Road Training

• Nutrition
  You've got to eat, and eat right if you expect to be able to perform well. Any rider that is trying to develop better performance such as longer lasting endurance, as well as greater speed, power, energy, and vitality from within themselves should eat well with a balance of Carbohydrates, Fats and Proteins, along with consuming generous amounts of water (as mentioned above) to ensure they remain well hydrated and in their best performing health base.
• Strength Training
  This is an important facet of training for motocross and off-road disciplines such as GNCC racing as it does require quite a bit of strength to be able to hang on to and maneuver a dirt bike for a hard charging 30+ minute moto, or 2+ hours in the most brutal off-road courses, so be sure to give attention towards strength training.
• Cardiovascular Conditioning
  This is one that is good to stay on top of and can be done with cranking out mileage riding a bicycle, playing court games such as tennis or basketball (among other sports), as well as running or jumping rope. To be beneficial you should maintain a target heart rate for at least 30 minutes. The target heart rate is between 85-90% of the predicted maximum heart rate which equals 208 minus 0.7 times the person's age. EXAMPLE: A 30 year old should have a maximum heart rate of 208 minus 21 equals 187. Thus the target heart rate would be between 187 times 0.85 and 187 times 0.90 thus equaling a target heart rate between 159 and 168 beats per minute.

• Flexibility
  Stretching is important and something that a lot of riders do not give much attention to but should. Stretching before any type of riding has many benefits and can help to prevent back injuries and other problems such as torn and sore muscles, so be sure to spend time stretching before kicking your bike to life or leaning on that "Magic Button", as well as once you put the dirt bike away and while your muscles are warm.
• Rest
  You've got to rest and allow your body to recover a few days a week, as your muscles and other body systems need time to recover between workouts to enable the best results and cannot properly do so with repeated stressing and no recovery periods in between.

Additional Motocross Training Resources

• Hydration Advice and Tips On Measuring Water Losses