Preserve any and all evidence of where the animal was or has been. Walk next to the animal's trail, not over it. Stomping over the blood and tracks you are attempting to follow will hurt you big time if you need to work backwards and I'd always rather be backtracking over the animal's prints than my boot prints, though if you're just retracing your steps your boot prints can still show you where you've already been.
Mark the blood everywhere you find it whether this is with flagging tape or a stick in the ground or whatever...it is invaluable to be able to glance behind you and see a figurative line in the dirt of where you came from to help determine where you might be going. OnX points can be handy as well but I like to have real, physical markers at each point I may want to revisit, or at least 3 or 4 in a row that can then be leap-frogged each time you find a newer sign.
Pay attention to the tracks near the blood and precisely what direction they are going as a small change in direction can lead you off course fairly quickly. If you don't immediately see the next blood from where you are standing, look up and forward rather than staring at the ground...it often becomes pretty obvious what is the path of least resistance which is often what a wounded animal will take. Additionally, not all blood will end up on the ground, and looking forward can help you spot blood and hair that may have ended up on taller foliage, logs and stumps, branches, etc. On top of that, don't forget that at any time you may have line-of-sight to your animal whether dead or wounded and still moving. It is easy to get stuck with your nose to the ground when searching for tiny drops of blood, but you may look 100 yards in front of you and be able to put eyes on the animal. I was tracking a wounded elk with some friends one time and my eyes were so glued to the ground in front of me that I would have walked right up into the bull if one of them didn't put their hand on my shoulder...we put the kill shot on him from no more than 5 yards away.
If you have good blood and tracks at the initial site of the shot, take mental note of what the kicked up/fresh dirt looks like compared to the settled ground around it. When you lose blood and resort to following tracks/trails alone, look for the dirt/tracks that look different or stand out. Deer and elk dig deep enough in almost any ground that a very fresh track will have a different moisture level than the surface around it.
Keep in mind that a running/bounding deer or elk covers a lot of ground very quickly. A stride or two for the animal (especially elk) may be several steps for you, and they may take several of those strides or leaps between spurts of blood.
At the end of the day, a lot of it comes down to being patient and not giving up. If there is blood on the ground there is a wounded animal ahead. It may or may not be dead, but you will never know if you don't keep following the trail.