First, make the shot count! If you can't hit the heart/lung area then don't shoot!

If the shot was bad, wait several HOURS before taking up the trail. Look for itsy butsy drops of blood. Sometimes they can be the size of a pin head. Look for turned over leaves. Look for the easiest route. Look for blood on the sides of taller plants. Take your time. If the deer is dead it won't go anywhere.