To carry on what Beentown mentioned above, and with the assumption that you're about to track a deer that you did not see drop.... never, ever, ever take up a blood trail without your bow (or gun) in hand. Even after giving a deer time, sometimes they don't die as quickly as the tv shows would like us to beleive.
A few years back one of the guys at deer camp shot a really nice buck. We all returned to camp, listened to the story, ate dinner, then headed out to get the buck out of the woods. With lanterns & flash lights in hand about 5 of us were on the blood trail. Tracking was no problem, we had good blood to follow, and came upon the deer within short order. Only problem was that the deer picked his head up and looked directly at us.... OK, get over here and put another arrow in him... "Oh crap, my bow is back in the truck!" says the guy. He and another turn to walk back and get his bow while the rest of us move back and wait. Well, the deer had one last burst in him, and in an instant he gathered his legs up and bolted. We backed out of the woods after that, and waited till morning to go back and pick up the search. Later that morning the deer was finally recovered, but we all made it a lot harder than it should've been by not taking a bow in with us.
Another time, I got a call from a buddy to come help him drag out a big doe. He felt that he put a good shot on her, and heard her crach down in the bottom behind his stand. I finished dinner, grabbed my light, and headed out the door. About 30 minutes later I was at the farm where he was hunting, and we drove back through the field to the woods. We were just about to head into the woods, and I reminded him to grab his bow, thinking back to the time at camp a few seasons earlier. We had good blood again, and tracking wasn't too tough. Then all of the sudden, I shined my light in the direction that the blood trail was heading, only to see a bedded deer pick her head up and look back at us. We backed out and let her lay, knowing she was hit hard but just needed more time. We came back the next morning after giving her overnight, and recovered her in the same spot.