With the enaction of Decoder Circuitry Act of 1990 (requiring all TVs 13" or larger to have a closed-captioning decoder built in), buying a TV became a lot easier for captioning users.
Fifteen years later, there's been quite a few changes in what constitutes a "TV." Now a TV isn't always just a single box that contains the tuner, display, and decoder. For example, a TV could be a plasma monitor hooked up to a satellite receiver. Where is the captioning toggle in such a set up? (See the FAQ page for more on that particular situation.)
So here's a short list of simple tips and suggestions to help make your TV-buying experience a little smoother and hassle-free.
Volume display: When you turn up or down the volume, does the volume meter temporarily turn the captions off? If this is a pet peeve of yours, look for a TV that doesn't do this.
CC on remote: Does the remote contain a CC button? Little things can go a long ways to making life easy, particularly if you live in a household where some TV users like watching with the captions off.
CC3: If you like watching Spanish captions of English-language shows (when available), your TV needs to have the CC3 channel. A lot of TVs only have CC1 and CC2. So be sure CC3 is an option before you buy.
Audio Description users: You need a stereo TV with SAP capabilities. Look for one that has an "SAP" button on the remote, as menus often are not described. (Sometimes SAP is called MTS, or Modular TV System, so that label may be used on some systems.) If that is not available, then try to find an easily navigable menu system.