#1 Blue flag tape tied to the wire.
#2 Kill more deer. My problems have went way down the last few years with winter kill and heavy hunting pressure. But make sure your eliminating does, not just bucks. On one single 160 acre property the last number of years, the hunters went from 16 kills, to 11, to 4 and just 2 so far this year. Over 1/2 the kills each year are does. My terms are if they focus on bucks only, they get the boot. Reduction of the herd is my #1 priority, not making sure some guy has a monster buck story to tell his buddies. The guys who have been here for a number of years follow my rules and as such, I try to make sure they have a good time each season.