Straddling the Bag
This method is used to turn a double play when the second baseman can get to the base early and the throw is made on target. The second baseman receives the throw with the base between his feet, then steps towards first base with his left foot and drags his right foot over the top of the base when completing the throw.
The straddle method is probably the fastest way of turning the double play, but it does expose the second baseman the most to the runner. If the runner gets to the base quickly or if the throw is a little late getting to the second baseman there is the potential for the second baseman to get injured. The second baseman should be sure that he has plenty of time when using the straddle method.
Balls Thrown in the Dirt
Sometimes, the second baseman will move towards the bag anticipating a double play and receive a low throw in the dirt. In this case the second baseman should act like the first baseman and ensure the ball does not get by him and try to at least get the lead runner. Making a double play is nice, but the main concern is preventing the runners from advancing and getting at least one out.
Avoiding the Runner
On double play balls the runner will be baring down on the second baseman. The second baseman's ability to avoid the runner will be instrumental in not just completing the double play, but also in preventing injury. When a second baseman makes the throw to first he should be sure that his toes are pointed directly towards first base. This will point his knee directly at the incoming runner and protect the more vulnerable side of the knee. After making the throw the second baseman should jump with his left leg to avoid the sliding runner. Even if the runner makes contact with the second baseman be getting his feet off the ground he is much more likely to avoid a lower body injury than if his feet were planted on the ground.
Covering Second on a Stolen Base
Since batters will normally pull the ball, the second baseman will usually cover second base on a steal attempt. This leaves the shortstop in position to field a batted ball. With a runner on first base the second baseman should shift towards the second base bag so he can beat the runner to the base if he attempts to steal.
On the pitch, if the runner is stealing the second baseman should sidestep towards second until the ball passes home plate. When the ball passes the plate he can run to the base. This will leave the second baseman facing the plate while the pitch is in the air, allowing him to field the ball in the event that it is hit.