For squirrels, get in the woods & sit. They're usually out just after 1st light unless it's real cold (it's in the single digits here now). If that's the case, they're gonna come out a little later.

For rabbits, I've got 6 beagles that will jump & run a rabbit back in a circle to the approx. area he jumped from. If you don't have beagles, that means you've gotta jump shoot them. If its super cold, they're often underground but if they're not, they'll be in the thickest, nastiest cover you can find. Lap/brush piles, briar patches, under downed trees, in thick overgrown fields/cutovers, etc.