The path of your club is very important and the body should be synchronized together. The most common swing path is the over-the-top move, where people swing outside to in. This will lead to fades, slices, and inconsistent hits. The plane of the shaft should react properly with your hands, and once the club is at the top of the backswing, should come down flatter with the hands coming from the inside, to out. When a player takes the club back inside to out (the slicer), it creates a slappy shot and there is lack of control. The swing plane that is inside to out, will allow for a more free flowing swing and more consistency. 

When speaking of a flat backswing, this means that as the club is on the downswing, the hands should be level as though you are holding a tray. You don't want to spill the imaginary food off that tray. Make sense? Here's another example. The normal straight shot, is taking it back and through on the same plane and allow the club path to mirror the back and through swing. The steeper you take the club back, the more likely your chances will be in hitting across the line and slicing the ball. 

You can also change the shaft angle of the plane without changing the club path. A drill that you can do to stop this from happening, is to put a club head cover under your right arm pit. When you take the club back and through, you want to hold that head cover in there as long as possible, allowing it to fall to the ground once you've hit the shot. You can also take the club back, hold it at the top of your back swing for a few seconds, then hit the ball; feeling the control and keeping the path correct. 

This basically comes down to where your body and arms naturally take the club back, so try to get out of the habit of being perfect, and start to build a solid foundation. Back and through, keeping the club on the correct swing plane.