Everybody slices (okay, almost everyone) and hitting the ball straight is one of the most puzzling things to learn. Let me clue you in to the six things you need to do to hit the ball straight instantly. I picked up the game late in life and, being the geek that I am, I became engrossed with the idea of how to learn to hit it straight. I am not the longest hitter by far, but what I lost in distance, I made up for quickly in accuracy and got to a 10 handicap shortly after figuring out these techniques.
There are only six things that are necessary to hit the ball straight
At this point, people usually say (I can't remember six things -- it's too hard). Well, quit whining, once you learn them, they become natural and you don't have to think again. The six things are:
1) Grip
2) Keep the club head low on takeaway
3) Feel tension on the inside of the knee on your back leg
4) Keep the club as far away from your body as possible
5) Rotate your forward butt cheek back to start the downswing
6) Aim to hit the inside, rear quadrant of the ball towards 1st base.
That's it. You see, you really only have to remember 2 things during the critical part of the swing. Let's break it down.
Grip
You need to learn the proper grip. It's been written up everywhere on the web and in magazines so I'm not going to repeat it here.
Keep the clubhead low on takeaway
This prevents you from "picking up the club" which is one of the main causes of the "over the top" motion. Put a tee in the ground behind the ball (about 6-9 inches depending on the club you are using) and knock it over when you taking the club back.
Feel tension on the inside of the knee on your back leg
If your feet are planted and you haven't swayed your hips, you will feel tension on the tendons on the inside of your knee on your back leg (I'm a righty so it's my right leg). If you feel no tension, you probably have swayed your hips and will end up slicing the ball. Tension means that you have rotated your body, not swayed.
Keep the club as far away from your body as possible
As you are winding up you should be feeling as if you are putting the butt of the club as far away from your body as possible. Two things will happen when you do this: you will keep your left (if you're a righty like me) arm straight, and you will be seeing the ball over your shoulder. If you are winding up correctly, you should see the ball over your shoulder.
Rotate your forward butt cheek back to start the downswing
Now that you are wound up, it's time to let it go. It starts from the bottom. If you rotate your butt cheek, a lot of good things will happen. You will not sway forward and you will set up the next move automatically (see, it's really not that difficult).
Aim to hit the inside, rear quadrant of the ball towards 1st base
This is something that people have problems conceptualizing and, to be fair, I read this on one of the golf boards and tried it. It turned out to be the last key I was looking for in my quest to understand the swing. If you picture the ball as you are addressing it with a crosshairs on top, you want to try and hit the inside back corner and hit it towards an imaginary first base. You won't hit it towards 1st base. Because the swing is a circle on an incline, it's easier to think of it this way. Trying to think "hit down the target line" causes you to swing over the top and you end up with a nasty slice. Thinking this way clears your head. You will find your divots are straight down the line.
(Plus one) Release the club
It's important to roll your hands and release the clubhead. This takes practice to get your own rythmn. You want to avoid breaking your wrists, but if you don't release the club you will mishit the ball. I practice by listening to the "whiff" on my practice swings and noticing when the sound shows up. If I hear it after I've passed by the "ball" on my practice swing, then I know I've released late.
That's it!
So, go try it. You will find that it's really easy to hit it straight. Once you can hit straight, then you can work on your distance. You may find that it's harder to add distance and stay in control because your instinct is to swing harder which will cause you to blow your technique. These 6 things are my way to remember my technique. When I screw up, I can tell you exactly what I did wrong.