For those of us who enjoy recreational and competitive shooting, positional shooting is part of everyday life. But becoming proficient at shooting from multiple positions will make you a better shot overall, so instead of avoiding those compromised shooting positions, you’d do far better to embrace them.
Not every shot can be taken from prone (the most stable shooting position), sometimes a shot requires getting off your belly, and finding another way to support your rifle.

Standing-
Standing is probably the most difficult shooting position for most, this is because being upright requires constant use of muscles to balance, as well as overcome any wind that might be pushing you around. If you include your own shaky stature it turns out to be quite unstable. There are a few things you can do to help solidify your shooting position when standing, one of the easiest is to add a sling. A sling allows you to create a rigid structure out of your upper body, by tightening your arms and shoulders against the sling. This Ridgid arch-like structure makes a more solid launch-pad for your shot.
Another way to improve your shooting from the standing position is to stop trying to hold still. While some folks can stand perfectly still, and make a shot, most of us (myself included) cannot. So instead of trying to stay completely still, you might be better off to embrace the movement. Many competition shooters use a pattern of movement instead of trying to remain still, they actually move their rifle on purpose, either in a circle or figure-eight pattern while aiming. By purposefully moving their rifle, they can absorb the unwanted movement caused by shudders and other influences, and the resulting pattern of movement is at least predictable. And predictability is where accuracy comes from.

Sitting-
Sitting is a common way to shoot when there is too much ground interference to take a prone shot. Sitting gives added stability, by bringing your center of gravity closer to the ground. This requires fewer muscles to maintain a steady position, and for many of us can be more comfortable as well. Sitting also gives us the advantage of using our legs for additional support, such as crossing one leg to use as a support for our rifle. This is one of the greatest advantages of all positions besides standing, the ability to use bone structure to support our rifle. Straight lines and triangles are what make a sound structure, so if we can build those structures with our arms and legs, and then fortify them with aids like a sling, we can actually get quite steady.

Kneeling-
Like sitting, the kneeling position brings us closer to the ground, requiring less muscle movement to steady our shot, it does however still involve a fair amount of balance. Kneeling shots are typically used when a sitting position is either too low or when a shot needs to be made quickly. As with other shooting positions, the most stable kneeling position is achieved when you create a rigid structure of bone. If you can, put one knee in the dirt, and one knee up. This will allow you some additional support for holding your rifle steady, the knee you raise may depend on terrain or just timing. Keep in mind that sometimes it’s the other knee that gives better support, so practice for each scenario to give you your best shooting platform.

Prone-
The prone position, or laying down is by far the most steady shooting position. This is because it requires no muscle movement,  a rug can lie still on the ground even in a brisk wind.
Shooting prone allows the shooter to completely relax, and focus all his/her attention on aiming, trigger control, and breathing. I mention breathing because when laid flat against the ground, the rise and fall of our chest can adversely affect our shooting. Both breathing and even sometimes the beat of your heart can register in the scope, both of these can be mitigated by rolling slightly to one side or the other. Another benefit of prone shooting is the ease in which we can use support aids like a backpack, or bipod. These kinds of support can greatly enhance your ability to steady your aim and make a better shot.

Support-
Since we mentioned bipods and packs, it would be a good idea to discuss how to use such support aids in our positional shooting. There are countless devices available to us today to help us support our shots, shooting sticks, bipods, tripods, bags, etc. They can greatly increase your steadiness when shooting. A tripod can make all the difference in the world when trying to steady a difficult shot from a sitting/kneeling position, and when you properly use your backpack for rear support when doing so it is ten-fold. Bipods and rear support bags can make prone shooting seem almost too easy, so easy in fact that many competitions try to limit the amount of shooting done from such a position.
Shooting from the standing position is immensely improved by adding the right height shooting sticks, as I mentioned earlier, it helps create straight lines and triangles which add stability. Depending on the shot scenario, even a rigid stick or tree branch can be used to stabilize your rifle prior to the shot. Do yourself a big favor, and research all of these options, and definitely try several of them out when practicing. You may find that getting off your belly was the best improvement your shooting ever received.

-CBM