toss, toss, toss! anything big that you want to get rid of put up on freecycle (we got rid of the swing set and old-deflated, gross out nasty dirty-above ground pool this way). if you have old electronics check and see where they can be dropped off and what the rules are (some places only allow a limited number per week).
make a "master plan"-pick a color for each category of packed items (kitchen, master b/r, master bath, other bath, office, kid room #1...) as you pack boxes put a peice of colored electrical tape on each corner (or all the way around) so that when you move again you can just post a chart for the movers to know what room each box goes into (also makes it easier if you have to pull something out of storage).
as far as moving costs go-price compare! i saved over $1200 on a local move using a larger company vs. a small independant. i also learned that when we move across country we can qualify for their much lower military/government rates (the rates they give to those agencies) by virtue of being retired government (they extend those rates to both active/retired gov. as well as retired military). some movers offer discounts associated with different affiliations (insurance company, real estate company, civic organizations...).
check into what insurance you will need for the move-i found that my renter's insurance will cover everything, same as if it were in my home, for theft or fire-any damage the movers do i have to have insurance through their company to cover. if you are moving on the holiday weekend BOOK A MOVER NOW! holiday weekends book up fast-and remember, some movers charge a massive premium to move on a saturday or sunday (ours would have charged 50% more). and check to see what their policy is on "wardrobes"-one moving company (the higher cost one) sold these, but the national chain brought them in for us to use at no cost (and then were nice enuf to let us keep them for a week so we did'nt have to rush and unpack them).
if you have valuables (jewlery, cameras-other small items) consider getting a safety deposit box at the bank local to where you live now. that way, when you are out of the area house hunting you don't have to worry about your valuables (and unless you have awsome homeowners or renters insurance to cover it-if you store it in your car it may not be covered or only covered very little).
when we move out of state we know we will have to drive our cars, so we will end up renting a couple of small enclosed trailers. i figure (god forbid) if something happened to the moving van there are certain things i could never replace (like photo albums and the like)-these along with basic essentials, enough to survive on should a moving van be delayed a week or so-will travel with us.
with our kids, i had both "personalize" a moving box (name on it, stickers, marking pen drawings) and put in what THEY considered essentials (for son it was his "cuddle buddies" he sleeps with, play station and games, and certain toys, dd packed her security blanket (well at almost 12 it's now more of a security rag

), some books, her cd player and cd's). this way we could recognize these small boxes immediatly and know they were not to go with the movers-they traveled in the car with us for quick access. also, if possible-STOP buying food! use up everything in the fridge and the cabinets. nothing is worse than having to toss perfectly good food out because you're concerned how it's been stored. i bought those multi packs of cereal the last couple of weeks-those were easy to toss into the kid's boxes for quick snacks while we were initialy getting settled. i also took to asking for extra catsup and condiments at the drive thru windows-they saw us through the first few days and i did'nt have to schlep the half full containers of ranch dressing, catsup and the like. paper plates and cups are also YOUR FRIENDS during the last few days pre-move (that way you dont end up with a bunch of dishes to run in the dishwasher and pack the last hour or so).
good luck-pace yourself so you don't get ill.