Another aspect of hitting that is important is the transfer of the weight from the back leg to the front leg at the moment of contact. Take a look at the pictures of the swings of Albert Pujols, Mickey Mantle (from both the left and right sides), Wade Boggs, Ted Williams, Derek Jeter, Barry Bonds, Rod Carew, George Brett, and Alex Rodriguez (some of the greatest hitters of all time). All are pictures of the hitters at or near the moment of contact, and note that in every case, they are hitting off a stiff front leg and their back toe is pointing straight down, either barely touching the ground or just above it. In other words, one of the things that made (and makes) these hitters great hitters is that at the point of contact, ALL of their weight is on the front leg, and none of it is on the back.
What I find interesting how many people who've been involved in baseball for a good part of their lives are unaware of this. Many believe that at the point of contact, some or most of the hitter's weight should be on the back foot (I hear Little Leaguers told this all the time -- "squash the bug!"), but as the photos below show, that simply isn't the case. Hitters should keep the weight back for as long as possible, but in the end, when they're about to ht the ball, their weight needs to shift forward.