What is the best cure for a headache?!

Headaches are caused by tight neck muscles so freeing them up is the way to get rid of it. Your neck muscles go to the top of your head where they connect to muscles that go around your head. When the neck muscles get tight they pull on the head muscles and when they go into pain you have your headache. Here's how to free up your neck muscles to get rid of the headache:
Neck
Put your hands alongside your head so your thumbs are on the front of the muscle under your ear and your fingers are on the back of the muscle behind your neck. Squeeze your thumb and fingers together and hold. Relax your body. When your fingers and thumb touch, about one minute, slowly lower your head as far as you can, release the pressure but hold your neck lowered for another 30 seconds.
For best results relax your body first by taking a deep breath and exhaling then remain this relaxed.

Depends on what kind of headache, if it's dehydration, drink water, if it's stress related, light Cardio, nerve damage, a glass of alcohol can do the job, and no joke, sex is great, because of the endorphins bomb that'll fix most forms of headache.

The answer is a bit too long to type out in the space allowed here.

But the answer can be read in the following book:

The MindBody Prescription - Dr John E Sarno MD

Drink loads of water. For me it's 2 painkillers and/or a nap. ;)

not getting one in the first place