Using a zero-turn mower gives a certain special pleasure. In the past, riding mowers have been clumsy, frustratingly slow and occasionally dangerous. But the zero-turn mower's wheels can be driven in the same direction at varying speeds to make a gradual, precise turn, or they can turn in opposite directions, causing the machine to spin, literally, on a dime. Here’s a guide for anyone interested in purchasing a zero-turn mower, including ratings from Consumer Reports’ Web site, Greener Choices (www.greenerchoices.org). If you regularly maintain several acres, you’ll be glad you went the extra mile to find the right tool.