The NY Times has a great article on stretching, dispelling the myth that stretching before you workout improves your strength / readiness. In fact:

If you’re like most of us, you were taught the importance of warm-up exercises back in grade school, and you’ve likely continued with pretty much the same routine ever since. Science, however, has moved on. Researchers now believe that some of the more entrenched elements of many athletes’ warm-up regimens are not only a waste of time but actually bad for you. The old presumption that holding a stretch for 20 to 30 seconds — known as static stretching — primes muscles for a workout is dead wrong. It actually weakens them. In a recent study conducted at the University of Nevada, Las Vegas, athletes generated less force from their leg muscles after static stretching than they did after not stretching at all. Other studies have found that this stretching decreases muscle strength by as much as 30 percent. Also, stretching one leg’s muscles can reduce strength in the other leg as well, probably because the central nervous system rebels against the movements.

Whoops! So quit it, y'all! This is obviously most important for athletes, who depend on their strength for their performance in sports. But it weakens muscles for everyone. Instead of static stretching, they reccommend something called dynamic stretching:

Stretching muscles while moving, on the other hand, a technique known as dynamic stretching or dynamic warm-ups, increases power, flexibility and range of motion. Muscles in motion don’t experience that insidious inhibitory response. They instead get what McHugh calls “an excitatory message” to perform.

Dynamic stretching is at its most effective when it’s relatively sports specific. “You need range-of-motion exercises that activate all of the joints and connective tissue that will be needed for the task ahead,” says Terrence Mahon, a coach with Team Running USA, home to the Olympic marathoners Ryan Hall and Deena Kastor. For runners, an ideal warm-up might include squats, lunges and “form drills” like kicking your buttocks with your heels. Athletes who need to move rapidly in different directions, like soccer, tennis or basketball players, should do dynamic stretches that involve many parts of the body. “Spider-Man” is a particularly good drill: drop onto all fours and crawl the width of the court, as if you were climbing a wall.

Read the article for more info and diagrams on how to improve your stretching routine!