Learn to hit good BAD shots
The difference between pros and amatures is not the good shots the pros make, but the bad ones.
We can all hit great shots that would be applauded at the Masters. But with a good routine the bad shots doesn't have to be a catastophy, but you can still make par and play your hcp.

 
Lear to play a GOOD round of golf on a BAD day
A pro has learned to accept that he will not always hit the ball where he wants to and will not always feel comfortable with the ball. In these situations he trusts his routine and keeps his mind on the good shots he's made in his carrer.

You might have heard Jesper Parnevik or other pros say that some days they just can't hit the ball straight, but slice everything. Instead of getting mad and try to change this they simply accept "todays shot" and aim a bit to the left for a slice or to the right for a hook or draw. There are many pros that have been able to win big tournaments this way even though they haven't been able to hit straight. In this case they just adjust their routine to fit todays shots.


Work on your routine to bring out your strong sides and a positive way of thinking.
A pro experiencing problems with his swing during a tournament usually spends hours AFTER every round just to work on his pre-sho-routine to remove any swingproblems and find his way back into a safe game.

There's most often something wrong with the setup, ballposition or grip that can be changed. The pro always goes back to his pre-shot routin and checks if there's anything that need changing that made a flaw appear. He uses his pre-shot routine to bring out his strong side and a positive thinking.

 
Visualise
Based on where the ball is going, the wind blows, what club you're using and what sort of swing you need to get the ball to the target.

When you've decided on these things the trick is to visualise the balls trip to the target. Do the stroke a few times in your mind and "see" how the stroke is going to end up.


Direction and partial target.
Learn to aim towards the goal with the help of a partial target.
The most important part in the pre-shot routine is aim. If you're aim is off you have to adjust your swing to make the ball go towards the goal. Taking out a partial target helps you aim your club to the goal. The line between the ball and the partial target is the line of play. The body and feet should be parallel to the line of play.

Taking a partial target is something almost 90% of all pros do and is a very helpful "aid" to set up correctly. The partial target can be a straw of grass, a pebble or a spot. If the partial target is too close to the ball the line of play might be incorrect and if it's too far away it might be hard to aim at.
The partial target should be somewhere between a half and a full yard away from the ball and must be in the exact line of play. It is an unbelieavable feeling of security to be able to stand above the ball and aim for a partial target knowing that you're aiming straight for the goal without needing to look at the same time.
Remember that the partial target only is and aid to help you aim. When you've set up to the partial target you have to forget the partial target and focus on the "real" target, where the ball is going.


Waggle
Making a waggle is pulling the club back 1 or 2 times before hitting the ball, to create a rythm, it brings a calm and the plane you wish for in the swing. I recommend to minimize the number of waggles to one and do the waggle the way you want your swing to start. Meaning straight back, low and preferably without bending the wrists. You can bring your wrists along in the waggle if you want, to soften them up, but you should always strive for a "one piece takeaway" where the body turns, arms are stretched out backwards for the best start of the swing.