Check multiple sites to find the best price. You might use a comparison sight such as Shopzilla.com, Froogle.com or Bizrate.com. These sites often offer reviews of items and merchants as well as prices. Also look for coupons at 247malls.com and MonkeyBargains.com.
If shopping through an auction vendor/merchant such as E-bay, always check their customer rating. Avoid any merchant with less than a 90% approval rating. Beware of merchants with bad reviews.
Use one specific credit card (your lowest interest rate card) for all online purchases so that if someone does get your card information, you will only have to replace one card. Internet purchases should be made using a credit card so that you can contest fraudulent charges or fees.
One exception to this rule is gift cards. Many stores allow you to shop online using gift cards that you purchase at their store. This will vastly reduce your identity theft risk but it commits you to shop in one place rather than hunt for the best price.
Only order through a secure (https://) server.
Order early so that you can take advantage of low-cost or free shipping.
Research a product before you buy it online. Know exactly what you are purchasing.