Afy,
You want 3 days basic needs ready to go. Protein bars, water, first aid kit, flashlight (batteries), matches, some clothing, a useful tool or two, maybe some rope, communication device (batteries) etc.
Vital documents... depending on reason for leaving and proposed duration, might include I.D., birth cert., home insurance policy, etc.
Mostly stuff to keep you going til you get to where you're getting. Should your home be in the way of extreme unpleasantness which might destroy it and it's contents, you get to choose what else gets to go along for the ride making sure that they're items you'll need to help you carry on post-disaster.