Control your breathing. When you start to panic, you might hasten your breathing, or hold your breath, both of which will make you more anxious. Focus on taking slow, deep breaths.
Loosen your grip on the arm rests. Let your body go limp. Tension will only make things worse.
If you are panicked or scared, watch the Flight Attendant. If they are calm and relaxed, it is good indicator that everything is OK.
Use the Emotional Freedom Technique (EFT)
Meditate - Try to Ground and Center
Perform Self Hypnosis