1. Ensure that you're entering your payment details on a secure site. Search for "https://" inside the URL of the site that you're trying to buy something from. If you don't see that or no sign of any website security, then it's probably a good idea not to trust those people along with your account information.
2. Make sure to read all the information about any product you are considering purchasing. Just looking with a picture online can be deceiving sometimes. It will make a product look bigger or smaller than it is. Make sure to look at the description so that you know exactly what you are actually purchasing.
3. Always save copies of your orders and receipts from online purchases. Many stores will redirect one to a page after you've submitted a purchase detailing anything that was bought, customer information, the prices, etc. You should either print a duplicate of this or save a copy to your computer in case any issues arise before the end of the return period. Make sure to save any emails regarding your items' status or correspondence with the company regarding your orders, too.
4. Before making a purchase, compare costs on several websites. Try to find special coupons and offers on these websites to successfully are getting the best offer possible. Also look into what it really will cost for the shipping on your own items and when there are free delivery options open to you.
5. Read customer testimonials before you buy anything. People are more than happy to complain about bad service online, so search for sites and testimonials which can be terrible so you know what you're getting into. You need to take bad reviews with a grain of salt, but if you see many, you know there is a problem.