Always compare prices in several online stores before purchasing an item. If you are not brand-loyal, you will also want to compare brands. Choose one with the right features and price. Go to the stores you like, since a lot of the time new products are rolled out.
If you shop online, avoid giving out a Social Security number. No site needs such information in order to sell you something. When they ask you for this, they are trying to scam you. Click out of that site, and go to a site with good reputations.