Another thing that I spoke about last class, and which I often remind people of, is their backswing.
Most people who have a problem with their backswing, tend to swing back too far. When most people do a large backswing, they swing back much further than 45 degrees for men, and vertical or 90 degrees for kote. Often they swing back to 0 degrees, meaning totally flat behind them, or even further. There is no real problem with this, other than it means your shinai has to travel further than necessary.
In kendo, 45 degrees and 90 degrees are considered a kihon backswing. Your backswing never needs to be bigger, and in certain situations can be smaller than this.
Again, for visual learners especially, please consider the diagram below.
The test of whether your backswing is big enough, is whether you can see your opponent's target area (datotsubui) beneath your left hand.