If you're going to be doing the packing, make sure to give yourself plenty of time in advance. The last thing you'll want to do on moving day is worry about where to place your belongings.
If your moving company will be assisting with packing, make sure they come over a couple of days in advance to prepare everything. Check to see if they're using high-quality packing materials - generally this should be discussed prior to the actual packing day(s).
Be present when the movers are packing your materials - movers are generally not liable for any damages that your belongings may incur, so watch carefully as they're packing to see if you'd like something packed differently.
Keep an inventory of everything that's going to be packed and included in the move. Give one to your movers, and make sure it is signed by both parties.
Consider insuring your more valuable materials prior to the move.