I learned this from my step-grandfather who is partly Erie Indian (looks like Abe Lincoln though). Most effective to trail walking-wounded, but works with others.
1. Find first good track and the second of the same foot and jam a little stick (or use stones) in both.
2. Get a stick long enough to span the distance between both and break it to match.
3. Lay end of stick in last visible print and pointed towards direction of travel.
4. Search for evidence of next (same foot) track near the end of stick. Often its nothing but a slightly dislodged bit of litter.
5. Repeat 3 & 4.
After awhile you can get real good with this and begin to see the track evidence without the stick. Also with a severely wounded animal, you may have to shorten the stick as it slows. In areas with lots of ground litter, you can get down on your hands and knees and look in the direction of travel. Often this new angle of view will suddenly reveal a huge length of tracks, especially if you now know the stride length to look for. Jam your stick into the nearest track for reference and move to the last one, make a new stick and start over.