flagging tape, hydrogen peroxide are must have's. I like the TP idea too.
I will almost always go immediately to the spot the animal was standing when I shot and start looking for blood and signs of a hit then follow it to where I last saw the animal. Whether I follow any further will depend on a number of factors... How much blood if any and what does the blood look like? did I hear a crash like it fell down in a heap or did it keep running for a bit. Make note of the direction of any noises i hear. Were other animals with it? Did i see the shot hit or not and if so, where was it hit? Was the animal aware of me when I shot?