Make a list of all the things you currently want to upgrade, and anything that you think will need an upgrade in the next few years. Start out by performing triage -- order them in terms of what most needs upgrading, with the neediest item going at the top of the list. Then rearrange your list in terms of what you use most and what you actually want to replace -- there’s no use putting a new vacuum at the top of the list if you know it’ll never come out of the closet. Also, if you have a few items listed in the same room, put the most focal one at the top of the list -- that way, you won’t be later stuck decorating an entire room around, say, a toaster.
Set aside money each month in your “upgrade account.” Once you’ve got enough saved to make the purchase, go ahead! Then start your account over for the next item on the upgrade list.
When you upgrade your couch, don’t just think about your couch. Remember, it’s the same couch you’ll have when you eventually upgrade your carpet, chairs, TV and everything else in the living room that you plan to, so make sure it’s something you can live with for a long time and something that you’ll want to decorate around in the future. Even if it’s something that lives independently -- say, a car -- think about what you’ll use it for three or five years down the road. Do you want it to be kid-friendly? You get the idea.