1) Drive on the right side of the road. Just because you're in a parking garage, doesn't mean you've been transplanted to London and it's suddenly okay to drive on the left side (or in the middle).
2) When making a turn around a corner, do it so that you end up on the right side of the road. If you're turning left, why would you cut it so close that you're on the wrong side after making the turn? You're just asking to be t-boned.
3) Drive slowly. There aren't cops with radar guns in the garage, but that doesn't mean you should speed. People do have to walk (or hobble) to their cars, you know.
4) When you get to an "intersection," slow down and look both ways. You don't automatically have the right of way, and sometimes other drivers are having a hard time seeing around parked cars.
5) Only take up one space. I don't care how expensive or shiny your car is, it can still fit in one space. In other words, this is not appropriate:
(I bet they can't color inside the lines either)