I can give you practical tips and theories 'til Jesus comes back, but without understanding why you are cluttered in the first place AND MAKING PROFOUND CHANGES in your actions, your home will continue to look cluttered and you'll think my tips don't work.
There are many reasons why people become and remain cluttered, and I discuss those in my upcoming book. One example is shopping for pleasure. Shopping can be an enjoyable and stress-relieving hobby. The problem I see with shopping as recreation lies in the results of shopping: the clutter in your home. If you continue to shop for recreation and bring your purchases home with you, your home will continue to stay cluttered, no matter how many handy tips I give you.
If shopping as recreation is one of the reasons your home is cluttered, then you can set limits on what you allow yourself to buy and bring home if you want to live a clutter-free life.
The easiest limit to set in regards to shopping is the "one item in, one item out" rule. When you purchase something new, get rid of (trash, recycle, or share) a similar item. When you buy a new book (CD, pair of flip flops, bottle of perfume, pair of sunglasses), let go of an old one. This way you will never add clutter to your home.
Another alternative for recreational shoppers is to buy things to immediately give away. You will still enjoy shopping, your purchases with be used and appreciated, and you will feel happier by giving. A great sale on winter gloves and hats? Buy some to donate to the homeless shelter. Found a like-new baby stroller at a yard sale? Purchase it to give to a single mom. Found a clearance on good, Christian books? Buy them and donate to your church's library.
You don't need to give up a cluttering habit or hobby; figure out how to enjoy it without adding clutter to your life.