Practicing with my bow also helps with estimating distances while upland hunting. I have 20, 30, and 40 yard pins on my bow, and practice shooting targets at those distances. I think it helps carry over to upland, since I am accustomed to what 20, 30, and 40 yards "looks like" from a standing position.
For all other types of hunting besides upland, whenever it is practical, I pace off the distance to objects in my field of view so I have a good idea of what distance I am shooting. If no obvious objects are there, I will pace off a decoy or even jam a stick into the ground.