You probably hear all the time about how bad having too many swing thoughts can be? They can destroy even the best natural swing. However, if you are trying to improve, you are inundated with swing tips and online coaching in this fast-paced media driven world. As I have tried to improve over the last ten or so years of serious golf, I found that it was just too much to remember and act on all that great advice while swinging a club. 
Pre-shot routine:
What works for me is to break the shot down into a couple of definite sections and assign specific thoughts to each. For example, with the driver there is my specific setup routine, not a thought but a deliberate way to get ready to hit the ball. I always stand behind the tee box facing the target, take my grip and 3 free loose swings while looking at the target. Then I pick a stick, piece of different color grass, something to align my ball to the target. I take 3 steps in setting the face of the club in alignment to the target line I just drew, and we enter the second part of the swing, getting ready to go.
Getting ready to go:
Now I take my stance and go into my waggle. A waggle is a way of keeping that free and loose feeling I had in my wrists and hands when I was taking my practice swing. It is at this point that my one thought is alignment. I am looking at the ball and picking out a specific dimple on the back of the ball (driver). Once I have acquired my dimple, I try to feel loose and as relaxed as I can get before a tee shot.
Final one swing thought:
Now I am ready, at this point I have done my homework, I know where I want to hit the ball and I know where I want it to go, and I have done a consistent routine to get all system ready to fire. So I have one specific swing thought for the type of club I am swinging. If it is the driver, 3 wood, hybrid, 3 iron – 6 iron, my swing thought is, “keep my hands as far from my head as I can throughout the swing.” If it is a short Iron, my thought is, “pull down the handle first.”
By having only one actual thing to think of just before and while I swing has made a huge difference in my game and my confidence in the shot, especially with the driver and woods. But what do each of the swing thoughts do for me specifically? My thought about keeping my hands as far away from my head as possible throughout the swings has had a big positive on my driver distance and consistency. By keeping my hands away from my head, I create a much wider arch for my swing resulting in greater clubhead speed and, for me, greater control of the ball. I will say, you have to practice it to really groove it and be able to trust it on the tee. It keeps me from getting quick with my swing and when I do it right, it feels like my swing has actually slowed down, but I have seen it on the scope, it is actually about 3-5 MPH faster! Even though you are keeping your hands away from your head, make sure you keep a light to medium grip pressure. Here is a short slow motion video, showing my driver from the top of my swing.
The thought for the short irons, “pull down the handle first” keeps me from, “casting” my irons, or firing the wrist and hands too soon. This thought has greatly improved my ball striking and helps me compress the irons more. This one will make your irons feel much quicker. So I know, one makes you feel slower with the driver, and the other makes you feel faster with the short irons. Both require some getting used to, and they are my swing thoughts, try to find yours but try to keep it to one thing while your actually swing.
For what it is worth, breaking my swing down into finite sections, and assigning specific thoughts to each section, had greatly de-cluttered my mind while on the tee box. But at the same time it has given me a repeatable process to get ready to hit the ball without a bunch of random tips running through my head. Try it, let me know if it works for you, or if you have a variation to share.