Well, I have had good results from "Whacking" the drive with a good hard thump to the side of the case with the hand during start up.

This can help overcome the "stiction" of the head solenoid and mechanics if it is not pulling in.

I'm not joking: I have managed to get a disk running like this, and pulled everything off it (thank the respective Deity). However, it's very much a one-time thing.

Another good one: stick the drive in the fridge, chill it down, then bring it out cold and put it in the machine again. Let it warm up to room temp for an hour, try again.

Otherwise, buy another of the same model, swap the controller board: this will let you know if the problem was the controller. Sometimes the drive electronics become unable to source enough current due to subtle damage, and a new board replaces the old one to good effect. It's finding the drive that's the problem.

Of course, you are knackered if it's a mechanical problem.