Similar to Tartan, I suggest starting through rooms and closets except....pick out what you have to have in your new space and mark them or put them aside...if you start by trying to decide what to get rid of/what you don't want, the decisions are harder to make. By thinking about the new place and what you want around you, you're addressing the move in a positive way and are able to make sure you have the most important things first. Once you've determined what you WILL keep in a specific room, then get rid of the rest. You can make some of the changes now, and by making decisions in this way you'll still be living with the things that really count. You still may end up with too much for the new place, but further paring down will be easier.