1. A reputable online seller should have a history that is recorded with the Better Business Bureau. Check with the BBB prior to deciding to part with your hard earned money to determine if there have been any major or continual complaints lodged against them. You don't desire to be spending your money using a company that fails to deliver.
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 look for these codes will allow you to insert the code at checkout to save money.
3. Be sure that you're entering your payment details on a good site. Look for "https://" within the URL of the site that you're attempting to buy something from. If you don't see that or no indication of any website security, then it's probably a good idea not to trust those people with your account information.
4. Never give out your Social Security number for an online merchant. This number is not required for placing orders online. Giving an online store your Social Security number can help them use your personal and private information to steal your identity. To prevent that, if you go on an online store site and see that as a requirement, tend not to buy everything from them and shop someplace else.
5. Be skeptical of overdoing it. It is much easier to overspend if you are shopping online. You begin to rationalize that you can spend more for those shoes because you saved money on gas and the food you would have gotten should you went to the mall, for instance. Give yourself a limit and follow it.