I listen for sticks breaking. I hunt in and around pine thickets and can usually distinguish a deer walking from squirrels. To me, a deer walking has a purpose. Squirrels and other small animals sound to me as if they are walking on top of the leaves. Having said that, my eye sight is better than my hearing and I usually spot them before I hear them.
Something you might want to consider is to mentally get in the hunt. Texting and playing games distracts me too much when I'm hunting.