Just thought this may be of help to anyone who shoots long end.

Explanations here http://digital-photography-school.com/how-to-avoid-camera-shake/

Several of those are just like the positions I took on the firing range in the military. Same purpose, reduce the shake. Breath control is also important when in most of these positions. Some advocate take a breath and hold it, others to release your breath (exhale) and take the shot (photo) at the end.

Breathe Like a Sniper to Take Better Photos in Low Light

The mantra for sharpshooting is "breathe, relax, aim, squeeze." In other words, breathe in, and as you relax your body and exhale bring your sights up on to target. You should come to your target just as your breath runs out, and slowly and steadily "squeeze the trigger" in this case I'd lightly depress the shutter release.

A camera strap is helpful if the arm is run through it and it's pushed back by the elbow. Just putting a strap around the neck and pushing forward until it's tight will also help some people.

This is for Tywais, works with a camera too. Everything Tywais said is what I learned too.

Having an image stabilised camera or lens helps too.

Trees, telegraph poles and walls should be number 7. Just jam the camera up against a solid surface

For stationary record shots there is often (well say one third of the time) something solid close-by - digital screens make taking such a shot so much easier than the days of look-thru-eyepiece only cameras,.