Use the “one in, two out” rule. The rule: whenever you bring in an item, you have to throw away two other items. First you cheat, by throwing out two pieces of paper, but soon you will have to move to big stuff.

Clothing rule: If you haven’t worn an item in 6 months, sell or donate it.

Have someone else (who you trust!) help you go through things. They don’t have the (sometime’s irrational) emotional attachment that you might have, but can still recognize if something should be kept.

Source: http://zenhabits.net/15-great-decluttering-tips/