Always leave it in first gear when parked on an incline..
This! I regularly had to push start mine due to a dodgy starter motor. It made parking it a pain as you had to make sure it was facing downhill if possible.
While we're on the subject, I lament the loss of the 'banger'. Kids these days don't know they're born with their fancy "cars that actually work". Where's the fun in the damn thing starting, driving in a straight line, being able to do more than 35mph without shaking itself apart, and not cutting out at every set of traffic lights, eh?