Most people have two kinds of clutter: memory clutter or "I-might-need-it-one-day" clutter. However, we all struggle with the 'lazy clutter' and that's what we need to tackle first.
Lazy clutter is all the stuff that accumulates out of negligence over time. It's not stuff you care too much about, so you ignore it: un-filed papers, unopened junk mail, magazines, unwanted gifts or that freebie cap you brought home from the grocery store but will never wear. Lazy clutter is little more than trash and one of the few purposes it serves is to accumulate on every flat surface in your home.
Memory clutter reminds us of some important person or event or achievement in the past—it's sentimental and often hardest to part with. "I-might-need-it-one-day" clutter is all that stuff that you know you might need...maybe. For the kick start, don't make the tough decisions that come with dealing with memory clutter or "I-might-need-it-one-day clutter." The first step is to take on the lazy clutter, then go through your other belongings methodically and logically. You'll learn how to balance the stuff you want to own with the space you have for it. When you find this balance, you'll learn how to keep it.
For now, stick to the quick-and-dirty purge and get rid of the superficial stuff that is relatively easy to clear.
Go to step 3: Think F.A.S.T.!