Carry a tube of moisturizer and apply frequently. A great alternative is a canister of Evian spritzer, which will do wonders for your face. Avoid alcohol or, at the very least, drink in moderation. The reduced oxygen on the plane intensifies the effect of alcohol in the bloodstream. Also try to curb caffeine intake.
Disposable earplugs are huge insurance against in-flight disturbances.
Drink plenty of water. Remember to stretch. Isometric exercises for your neck, hands and feet work well in the confined space of an airline seat. Unfortunately, this pricey equipment carries the same allure to thieves. A common trick criminals use to get laptops is snagging them from stalls in public restrooms at airports, hotels and other buildings where business people are likely to be.