1. Hug someone. Giving a hug means getting one. As long as it's from somebody you don't mind hugging you, this really can be relaxing.
2. Interrupt routines. Go talk to that man sleeping on the bench, or eat lunch on the roof. Just doing anything that breaks you out of your habitual patterns can relieve stress.
3. Have a hot shower. It relaxes your muscles, and any break from more stressful activities can help too. Some find that an alternating hot and cold shower is even more relaxing.
4. Try watching your mind. Spot the stresses lurking just below the surface (hunger, worry, money, a phone call you need to make, a deadline to meet), and you can resolve them and feel more relaxed. If you practice this mindfulness exercise, it may become one of your favorite relaxation techniques.
5. Try laughing. Your own experience shows that this helps you relax, right? Go find someone that knows all the best jokes or just has a great sense of humour, or find something funny in front of you.
6. Use relaxing music. Keep your favorite relaxation CD or MP3 at the office, in the car, or wherever you'll need it most.
7. Leave the room for a while. This can really help if the things in the room or related to it are triggering your stressful thoughts. Why not get out for a little while?
8. Breath deeply. Try five deep breaths through your nose. Close your eyes and pay attention only to your breathing while doing this. It's like a mini-meditation, and perhaps the most effective of the quick relaxation techniques.
9. Drink some chamomile tea. Chamomile tea seems to have a calming effect on the nerves. Any hot tea without caffeine may be relaxing.
10. Walk a while. If you have at least ten minutes to spare, walking is one of the best relaxation techniques. While you're at it, find a pretty place to walk.
Naturally, it is ideal if you can change yourself, so you're naturally more relaxed all the time. Perhaps the thought of the work involved in this just stresses you more. In that case you might have to take it slow, so why not start with one or two of the simple relaxation techniques above and then slowly progress to meditation?