I have a solid grounding in field positions from my competition shooting days, but I didn't have the confidence to make longer (as in 100 yards plus) but perfectly sensible shots from sitting and kneeling until I discovered collapsible shooting sticks such as those offered by Shooters Ridge. Over the years I've used them extensively, and now I never go on a big game hunt without them.
Made of lightweight aluminum tubing, the sections of the sticks are shock-corded together and are quick to deploy--just shake them out and they pretty much put themselves together. When folded up, they measure just 14.5 inches and weigh next to nothing.
The two legs pivot at the top on a rubber fitting, and you adjust the height of the sticks by spreading the legs to the desired position. This design is not only quick to use but allows the sticks to be useful on uneven terrain as well as flat ground. Conical tips keep the legs from sliding on terrain once they're positioned.
What I particularly like about the Shooters Ridge model, which I hunted with a lot last fall, is that the rubber end caps fully enclose the top of each leg. In open-top designs, I've found that, in time, the fitting on the legs becomes worn and allows the legs to slide when you put a rifle's weight on them; that can't happen with the Shooters Ridge sticks. $37.