Golf is a game that is supposed to be fun and enjoyable. The elements of pressure and competition get introduced early in the process, and that takes away the enjoyment for some--although it heightens it for others. Pressure shows up most often when the player is at the tee and on the green. Relaxing on the tee is one of the keys to hitting the ball well and getting it down the fairway with consistency.
Take care of the fundamentals before you even begin to swing. Start off by addressing the ball correctly. Your left shoulder should be square to the target and the side of your left foot should be directly underneath your shoulder. Play the ball about one ball length closer to your front foot than your back. Being in the right position should help you to relax before you begin your swing.
Watch others as they tee off on the first hole. You will usually see some of the worst swings of the day on the first tee, because players want to impress their playing partners by hitting a long drive on the first tee. They do this by swinging as hard as they can. This is a big mistake. A smooth, slow, repeatable swing is far more effective. You will see this if you watch two foursomes or more on the first tee.
Breathe normally when you get to the tee box. Some players are concentrating so hard that they stop breathing altogether. Others take long deep breaths. The correct thing to do is breathe normally.
Think about the rotation of your hips to get your swing started. You do not have to swing hard or move your arms through the ball violently to get a good drive. Instead, you need to turn your hips to the right on the backswing and to the left as you come through on the downswing. Do this, and your arms will follow.
Go to the practice range regularly and work on your tee shot. You will find by swinging smoothly and slowly, the ball will fly down the fairway with regularity and you will feel relaxed and powerful while hitting the ball. This is a far more effective way to hit off the tee than trying to overpower the ball.
Tips & Warnings
Tell yourself that your opening tee shot doesn't matter. This often helps players relax when they tend to tense up before hitting their first shot of the day.