One of the most tricky decisions (and expensive for that matter) for younger players is selecting the right bat weight and length.  The reason this is a difficult question is simply because there is no cut and dry answer. However, here are a few considerations to make as you search for the bat that matches your body size and baseball swing mechanics. 

First, particular attention should be placed on not getting sucked into the all too common fallacy that a bigger bat is always better. This is not always the case. For the duration of my career I was placed in the middle of the lineup for only a couple reasons, two produce power numbers and drive in runs. The biggest bat I ever used was a 33 inch, 30 ounce bat which is pretty typical of mature hitters.  Some players expanded a bit and used a 34 inch bat, but that was the exception. In fact, there were quite a few guys through college and on into pro ball who used small bats while hitting a baseball. The reason for this was simply that they were looking for bat speed because that is really what counts. If you want to create a good baseball swing, bat speed is important.

Secondly, while bat speed is valuable and should be developed, there is such a thing as a bat that is too light.  This then becomes counterproductive for a player. A hitter should always want to be in control of his body when swinging instead of it feeling like the bat is swinging him. If the bat swings like a whiffle bat, then it will be tough to maintain bat control while hitting a baseball. This usually occurs when swinging a bat where the weight is significantly less (minus 9) than the length of the bat.

Thirdly, try not to worry so much about if the bat is long enough to cover the entire plate. Most hitters who are hitting an outside pitch with the correct fundamentals will be able to reach the outside part of the plate with most bats. On the flip side, I’ve seen hitters with long bats that can’t hit an outside pitch because their baseball swing is flawed.  Even if the hitter is having a tough time covering the outer part of the plate because of bat length, chances are most pitchers will not be able to throw to the outside part of the plate consistently anyway. 

Finally, when selecting the bat that is right for you, rely on comfortability. Many hitters, even younger players, can pick up a bat and swing it and can tell if it "fits". I liken it to trying on a pair of shoes that are much too small. You can tell instantly that they don't fit, especially if you compare them with a pair of shoes that fit comfortability.