Stretching and Warm Ups

Hello,
So I mentioned yesterday that I would be putting up a post about one of the most IMPORTANT aspects of any physical activity; STRETCHING. I am as guilty as anyone for not stretching sometimes, but I am making a conscious effort to do it every time I go to practice. It is very important to have a good warm up as well. Today I will tell you about a good arm stretch and give you a detailed warm-up.
Arm stretches:

Place your right hand on you upper back, with your left hand push the right elbow down, and hold for 20 seconds. Repeat on alternative side

Find a wall, and face it. Place your arm at 90 degrees with your hand pointing upward, and twist your body until you are no longer facing the wall. IT IS IMPORTANT THAT YOU NEVER STRAIGHTEN YOUR EXTENDED ARM THAT YOU ARE STRETCHING, as this puts too much pressure on the shoulder.

Good warm up:

800 total:

-200 swim freestyle, stretch it really long and go slow.
-400 backwards IM, so every 25 of each 100 repeats swim, pull, kick, and swim.
-200 kick; first 100 freestyle, second 100 butterfly.