I hate, loathe, and despise yard sales, so I didn't bother with one. I sold the good stuff on Craigslist (which is still a nuisance, but we needed the money), donated a bunch of stuff, and still had to chuck out a ton. And this despite the fact that we were leaving most of our stuff in storage--I didn't want to have to mess with (or pay to move) all the junk later. I found that making an international move really changed my perspective on what to keep and what to get rid of. I'm not a pack rat for the sake of being a pack rat, but I am a bit of a guilt-motivated pack rat, as I hate putting potentially useful stuff in a landfill.
My OCD side got out of hand for this move, and I kept an exhaustive and minutely detailed list of everything that went into every single box. I kept it on my laptop, and typed up what was going in as I put it in. This was as much for me as for insurance and customs purposes--I wanted to know where everything was when I unpacked the stuff from storage in three years! So when it came to shipping stuff (we only had 10 boxes, so we just sent them through UPS) I just printed out the contents of those boxes and took it along. The UPS people loved me! They just attached those ten pages or so to the customs form.
Try to not think of the weeding-out process as one big job. Break it down. Take one drawer, pull everything out of it, and start sorting. Do you want to pay to move it? Can you think of somewhere that could use it? Are you going to be happy to see that thing in a box on the other end (this was really helpful for me!)? Then move on to the next drawer. When the drawers are done, tackle a closet. I found it helpful to have one room set aside for things to get rid of and another for things to take.
I've moved a lot (6 times in the last 6 years!) and I finally got sick of lugging around a bunch of rubbish. This was a good chance to get rid of all that. I made a real effort to keep only the things that were genuinely useful, meaningful, or beautiful, and that I would be happy to see again. But it's definitely not easy--you have to do some serious mental reprogramming.
Good luck!