The Relaxation Response was developed by Herbert Benson back in the 1960s. He experimented with the physiological benefit of a simple breathing and meditation technique. He found that when you focus your mind and calm the breathing, you get the following response:
Your metabolism decreases
Your heart beats slower and your muscles relax
Your breathing becomes slower
Your blood pressure decreases
Your levels of nitric oxide are increased

The relaxation response is very easy and only takes a few minutes. It has two steps in its practice:
The repetition of a word, sound, prayer, thought, phrase or muscular activity, and the passive return to the repetition when other thoughts intrude. ( Benson 162)

For an informal practice of the Relaxation Response, the sequence might go as follows:
Start with quick relaxation of all muscles: begin at the feet and work your way up through the body, tensing muscles and then relaxing them. Tense and relax the feet, legs, buttocks, groin, back, trunk, arms, shoulders; roll the head and relax the neck, and, most importantly, tense the muscles of the face and then let them go.
Take three deep breaths, and as you exhale, let go of any tension.

Now go into the repetition:
Choose a word, a sound, a prayer, or a phrase in your own belief system to repeat. Even a simple word will do: “one,” “peace,” “calm,” “om,” “shalom,” any word will do, it’s your choice. Then use a process of mental repetition to say; “I am relaxing the feet, I am relaxing the feet, I am relaxing the feet…the feet are now completely relaxed.” After you have worked your way through the body, close your eyes. On the in-breath and the out-breath, say your repetition…when you notice a different thought has come to mind, don’t get angry or stressed about it, but let it go and gently come back to your repetition. Repeat for 3 to 5 minutes. ( Benson 162)

This very simple and effective technique has been used by thousands of people! It is the cornerstone of the Mindfulness Based Stress Reduction programs that has been taught by Jon Kabat Zinn for over 20 years. Give it a few tries and you will find that in 5 to 10 minutes you will reduce your stress. If you do well with the basics and you want to move on with this, you can try visualization and/or meditation.