The goal of all hunters is a quick, humane kill where the animal drops in it's tracks and is dead within seconds. But in a pursuit that has as many variables as hunting, sometimes things don't quite go according to plan. However, game can be tracked and recovered with the right skills and with patience.
First of all, you need to wait the right amount of time after the shot before tracking a wounded animal. I've heard estimates of waiting 30 minutes for a hit in the vitals and 5-8 hours for a gut shot. Waiting overnight might be even better on very poorly hit animals. You don't want to push it. Be patient and wait it out. If you push a wounded animal, and he gets adrenaline flowing, the odds are against you finding that animal.
You need to mark the exact spot where the animal was when it was hit. This will save you much time in searching for blood. Also mark the position where you took your shot from in case you have to return to it to regain that perspective. Once you find the trail that the animal took after the hit you should try and identify where you hit that animal. Dark blood can indicate a liver or muscle wound; bright red blood with bubbles in it is a good sign and indicates a hit in the lungs; green liquid or bits of food matter in the blood indicates a gut shot.
Take it slow and mark blotches of blood with flagging tape every 25-50 yards to trace the trail from afar to determine overall direction the animal took. Just remember to go back and pick up the tape when you're done. You should walk to the side of the trail so as to not disturb the sign. If you lose the trail and can't find more blood, start fanning out and walking circles from the last place you had blood.
When tracking a wounded animal it is easy to get caught up in just looking at the ground, trying to find that next speck of blood. You should be aware of what is 100 yards out in front of you as well and be ready for a killing shot if the animal should get up in front of you.
If you take it slow, be quiet and be thorough, finding wounded animals can be done on a consistent basis. Follow these tips to help find the game that you might have not put the best shot on.