Although flat-panel high-definition televisions—whether based on plasma, LCD, or DLP rear-projection technology—have decreased in price sharply, they certainly aren’t low-cost impulse buys. Most of them offer a stunning picture, but if you don’t do your research, you could end up spending hundreds or even thousands on a model that doesn't meet your expectations. Before you splurge on an HDTV, check out our quick guide and some buying basics.