I try to calm myself down and breathe. I want to start exercising but I had surgery on my foot a couple months ago and it isn't quite healed.
I am in biopsychology in college right now and we've talked about meditation and practiced it too.
1. Sit in a chair or somewhere comfortable
2. Make sure your back is straight, rest hands on thighs, feet flat on floor
3. Close your eyes and breathe normally
5. Begin by simply being aware the chair beneath you. Notice how it feels
6. Next, bring your awareness to your feet and their contact with the floor
5. Be aware of every body part from your hands, to your head, step by step
6. You should feel very relaxed now. If not, it may take practice
7. Now, simply breathe
8. Be aware of your breaths going in and out
9. Either in through your nose or you can feel it filling up in your diaphram and then letting it out
10. Any thoughts that arise (like firkin said), acknowledge it but return to your breaths
You can do it for however long you like but it is very relaxing! If you find yourself unable to focus on your breathes and your mind keeps wandering, don't get frustrated because it is perfectly normal. It takes practice.
Also, I find that even steps 1-6 is relaxing in and of itself without the breathing if I am in a hurry