How to lower your risk of getting altitude sickness
1. Hydration - Drink plenty of water and stay well hydrated whenever you gain elevation.
2. Avoid Alcohol - Alcohol slows your body down and decreases the amount of oxygen in your blood.
3. Eat Carbohydrates - A high carbohydrate diet will help keep you fueled and feeling good at higher elevations.
4. Rest - Get lots of sleep and take plenty of breaks.
5. Get Acclimated - Give your body time to adjust to higher elevations. When gaining elevation try to spend some time at a 'medium' elevation for your body to adjust before heading on to a higher elevation.
6. Ginkgo Biloba - According to the CDC taking Ginkgo Biloba can help prevent altitude sickness.
7. Ascend Slowly - Take your time. Don't rush into higher elevations. Take it slow, if you start to feel nausea or headaches turn around before the symptoms get worse.
More information available here: symptoms of altitude sickness.