Timing, rotation, and weight transfer are essential to good hitting. The amount of rotation vs. the amount of weight transfer will vary from hitter to hitter. In general, power hitters tend to be more rotational, while single hitters tend to be more weight transfer. One mechanism to help achieve all of these is the coil. Simply put it's much easier to swing the bat and achieve better timing if you move back before going forward. As the pitcher starts his delivery, you will want to move your weight back on to the back leg, closing your shoulder, hips, and knee. This is also the point when you want to move the bat near the launching position. When the coil is complete you are in the correct position to stride.
One of the most common mistakes made by hitters at all levels is having the stride be part of the swing. In fact, hitters should perform the stride before the swing.
During the stride, you shouldn't transfer your weight from the back leg to the front. Hitters that transfer their weight have a difficult time handling off-speed pitches. (Looks like lunging at the pitch.) Having good hip rotation is a critical piece of the swing for hitting with power. For the hitter that transfers his weight forward with the stride, power is lost not only from the transfer of weight at the incorrect time but also from the inability to rotate the hips properly.
You may notice that a number of big league players do have the stride as part of their swing. The key for these hitters is the big leg kick, which acts as a timing device and doesn't result in the transfer of weight. Instead of picking their foot up and moving it forward, they're picking up their foot and hold it until they recognize the pitch. If they read fastball, they drop their leg quickly and swing. If they read off-speed pitch, they simply hold it there a little longer before putting it down.
The key is to stride out with the inside portion of your front foot. One way to think of it is to act like your striding onto a dozen eggs and you don't want to break those eggs. By doing that you will keep your weight back. Make sure you stride with your front foot closed. If you open up your front foot towards the pitcher, you will also open up your hips which will cause a loss of power when you do swing.