Whether to buy an extended warranty or service plan for a new gadget is a question most shoppers face. Now, with more players in the marketplace, where to buy one may be the more important question. In most cases, protection plans aren’t a great deal. Dan Ackerman, a senior editor with electronics review site CNET, says, “You’re going to spend more buying the warranty than you’ll get back [in protection].” Still sold on the idea? There are plenty of options. Manufacturers including Dell and Apple offer them, as do retailers such as Best Buy and Wal-Mart. There are also third-party sellers, notably SquareTrade.com . Before paying for gadget protection, make sure you aren’t already covered for free. Many credit-card issuers automatically extend manufacturer warranties on purchases made with their card.