Go here, and then bookmark it as well. A sample (but you REALLY need to read it all!):
Section I. ADVANCED FIRING POSITIONS
After mastering the four marksmanship fundamentals in the two basic firing positions, the next step is to master the four fundamentals while firing from a variety of advanced firing positions. The following paragraphs demonstrate the most common firing positions a soldier may be required to fire from. The firer's position may change but the application of the remaining three fundamentals applied from a stable position never changes. Ultimately, any firing position that aids the firer in applying the fundamentals is acceptable, as long as it is applied consistently each time it is used to avoid changing the firer's sight picture.
7-1. ALTERNATE PRONE FIRING POSITION
This position is an alternative to both prone supported and unsupported firing positions (Figure 7-1). The firer can assume a comfortable position while maintaining the same relationship between his body and the axis of the rifle. This position relaxes the stomach muscles and allows the firer to breathe naturally.
7-2. KNEELING SUPPORTED FIRING POSITION
This position allows the soldier to obtain the height necessary to observe many target areas, taking advantage of available cover (Figure 7-2). Solid cover that can support any part of the body or rifle assists in firing accuracy.
7-3. KNEELING UNSUPPORTED FIRING POSITION
This position is assumed quickly, places the soldier high enough to see over small brush, and provides a stable firing position (Figure 7-3). The nonfiring elbow should be pushed forward of the knee so the upper arm is resting on a flat portion of the knee to provide stability. The trailing foot should be placed in a comfortable position.
7-4. STANDING FIRING POSITION
To assume the standing firing position, the soldier faces his target, executes a facing movement to his firing side, and spreads his feet a comfortable distance apart (Figure 7-4). With his firing hand on the pistol grip and his nonfiring hand on either the upper handguard or the bottom of the magazine, the soldier places the butt of the rifle in the pocket formed by his firing shoulder so the sights are level with his eyes. The weight of the rifle is supported by the firing shoulder pocket and nonfiring hand. The soldier shifts his feet until he is aiming naturally at the target and his weight is evenly distributed on both feet. The standing position provides the least stability but could be needed for observing the target area since it can be assumed quickly while moving. Support for any portion of the body or rifle improves stability. More stability can be obtained by adjusting the ammunition pouch to support the nonfiring elbow, allowing the rifle magazine to rest in the nonfiring hand.
7-5. MODIFIED SUPPORTED FIRING POSITION
Once the basic firing skills have been mastered during initial training, the soldier should be encouraged to modify positions, to take advantage of available cover, to use anything that helps to steady the rifle, or to make any change that allows him to hit more combat targets. The modified prone firing position uses sandbags to support the handguard and frees the nonfiring hand to be used on any part of the rifle to hold it steady (Figure 7-5).
where are the figures or link?
Here's the whole Field Manual:
https://atiam.train.army.mil/soldierPortal/atia/adlsc/view/public/6712-1/fm/3-22.9/TOC.HTM (https://atiam.train.army.mil/soldierPortal/atia/adlsc/view/public/6712-1/fm/3-22.9/TOC.HTM)
talking with 'Damon' about positions and he gave me this site. I found it very helpful and enlightening as well.
http://www.tpub.com/seabee/2-27.htm