1. Apply pressure to the skin between your index and thumb (area on photo above) using your other thumb. The nerve in that area releases tension from the head, thus reducing the headache.
If you wear glasses, take them off and close your eyes or gently stare into the distance. Sometimes a headache can occur when a lot of stress is on the eyes.
Working too hard or too long? Take a break! Relax a little, spend some time outside, or just take your mind off of work and think of happy, soothing things.
Well, that's all I've got. Hope it helped!