1) Don't be afraid to shop at second hand or consignment shops! Often, people bring things in that they have never even worn, usually the tag is still on. You can buy these things for up to 80% off the original price!
2) If you have a smart phone, there are tons of apps you can download that have all sorts of coupons to a wide variety of stores. I use one called Snip Snap, which allows you to "snip" coupons on the app and "snap" coupons you already have and upload them to the app so you don't have to lug them around in your wallet.
3) Always head straight to the sales rack. Walk past the full priced items and go straight to the sale section. This will prevent you from splurging on something that will eventually be on the sales rack anyway.
4) If you are planning to splurge on something expensive, be sure to shop around. If you find something in the store, tear yourself away from it and do some research first! Most of the time, things will be cheaper online, or at another store.