1. If you find a great product on the favorite site, search for it in a search engine before you buy it. Make note of the model number or brand, and do a quick search to successfully can't have it cheaper from somewhere else. You might be able to save a few dollars like that.
2. Before going shopping at any online retailer, do a quick search for promotional codes. Lots of the big retailers often have promotions running which are not advertised on their own home page. Doing a quick search for these codes will allow you to insert the code at checkout to save money.
3. Always save copies of your orders and receipts from online purchases. Many stores will redirect one to a page after you've submitted your order detailing everything that was bought, customer information, the prices, etc. You should either print a duplicate of this or save a duplicate to your computer in case any issues arise before the end of the return period. Be sure to save any emails about your items' status or correspondence with the company regarding your orders, too.
4. Be wary of overdoing it. It is much easier to overspend when you find yourself shopping online. You start out to rationalize that you can spend more for those shoes because you saved money on gas and the food you would have gotten in the event you went to the mall, for instance. Give yourself a limit and stay with it.
5. For those who have questions while shopping, search for a live chat function around the online store. Many big brands (and even some boutique stores) now have this functionality. You are able to chat immediately with a customer support representative to correct any issues or answer any questions prior to buying. That can provide you with a lot of reassurance.