The best self defense technique pales in comparison to simple avoidance. Yesterday, a woman was sexually assaulted and robbed when a man jumped into her car as she was driving in a fairly nice shopping area. He assaulted her, made her go to an ATM and draw money, then had her take him to the nearby mass transit station where he made his getaway at taxpayer expense.
This could have been avoided by simply keeping the doors locked and windows up as soon as she got in her car until she got out. This is a basic thing we learn in Executive Protection training...you are your own bodyguard, so do it for yourself!