There are a number of key elements that go into executing a good golf shot and your backswing is definitely one of them.
How you take the club back will determine to a great extent how well you strike the ball at impact. If your backswing is on plane, you are more likely to come back to the ball on the correct plane and make solid contact. Conversely, if you are inclined to take the club back too far on the inside or to the outside, you will have difficulty bringing it back on the correct plane, resulting in a poorly hit shot that could leave you in trouble.
The most common backswing fault among recreational golfers is to take the clubhead back too far on the outside. The problem with this move is that it leaves the club laid off at the top of the backswing and promotes a downswing that also comes too far from the outside. This kind of swing usually results in a weak slice, the standard shot for high handicap golfers. There are simple drills you can do to ensure your backswing is one that will encourage a repeating swing, one that leads to solid contact every time. For example, try sticking a rod in the ground just outside the line you want your backswing to follow. The key is to avoid hitting the rod as you take the club back. A simple drill but one that works.
The same drill can be employed if your problem is taking the club back too far on the inside. Again, placing an object in the line of your faulty arc will encourage you to bring the club back on a better plane. This is something you can practice on the range or even in your back garden at home. Try to feel the sensation of grooving a backswing that puts your club in good position at the top. If you have been in the habit of bringing the club back too far outside the line (and most golfers do), it will feel strange for a while until you make this first move part of your regular game.
Another simple adjustment you can make to ensure your backswing tracks more on the inside is to open the clubface a little before you take the club away. This will promote a swing that is more on plane if your tendency has been to swing outside the line. You can spend all the time you want beating balls on the driving range but until you develop a good backswing, you will never hit the ball as you want. The backswing is inextricably linked to the downswing and must affect how you bring the club back to the ball. Improving your backswing will be sure to improve your game.