That is a great question.
1) Keep in mind, the deer that pass in front of your trail cam are not the only deer in the area, however they are the only deer that passed within 10 feet of the camera. You will get blank picks from time to time. There is a family of Armadillos that sets mine off all the time, and often all I get is a tail or a blur from where they triggered it. Wind also can trigger it if there are leaves or trees moving in front of it. If you trim down some of the foliage, it helps reduce the amount of times wind triggers it.
Since you are on a trail with your camera, you can help by setting it back a few more feet or put an orange flag or something in the trail, just anything to make them pause. That will keep you from getting pic's of deer butts all the time. Great site for trailcam info is http://www.chasingame.com
2) For deer, you want to be where they are when it is legal shooting time. You can hunt that trail all day, but if they only come out at midnight, or 4AM, then your odds of getting a deer on that part of the trail are bad. This could change as deer move more the colder it gets, so whats a dead spot today could be a hot spot tomorrow.
Two things you want to find out are where they are bedding and where are they feeding? If you have access to their food source, you can hunt the edge of that. If you have access to the bedding area, you can hunt the outskirts of that as well. I would not setup in the middle of their bedding area b/c you chance pushing them out.
It's a fact that 70 percent of the people who purchase heavier tackle do so with the categorical I just lost a huge snook! Einstein Hairdo.The other 30 percent have either Tarpon Fever or are sporting a hand cramped into a claw from a deepwater grouper.