This sort of sounds like a no-brainer, but don't pack things you absolutely have no intent on using in the future.
Clothes- what doesn't fit: donate. You can donate to your local church clothing swap, or goodwill and get the tax deduction. Freecycle is another good place! Get rid of what is ripped, stained or stretched.
If you haven't used something in a year- donate it!
is food going to expire in a few months? drop it off to a local homeless shelter.
If you live in an apartment, take advantage of your dumpster! throw out massive amounts of trash, that way when it comes down to it, you won't have to pay for a trash service.
Label everything! I have a meticulous moving system, and it's been known to drive people to madness. all I do is label every box (color coded) with what room it goes into. On a list in my Moving Binder, I put what is exactly in that box. That way I can list boxes of importance (dishes, over tchotchkies) and what boxes need to be opened first.
I'll have more tips to come later. :)