I walk real quietly and slowly through the woods. Around where I live we have a lot of grey squirrels with black fur, I can see those from a long way off in the winter when the snow and lack of leaves makes the black shape pop out at your eye.
Once I see one that I think I can approach, I stalk into range. At this point the squirrel usually spots me, and we start going in circles around the tree he's in. If he screws up and lets me get on the same side as him, lights out.
I find that in the winter when food is scarce squirrels usually can be found in 2's or 3's. If one runs to high, or hides somewhere I can't shoot I just stand still and listen. Usually I can find another more exposed one that way. An added bonus is sometimes the original squirrel I lost track off will get curious and pop his head out around the side of the tree. Then you gotta raise your bow real slow, pick a spot, and drop em.