Use maps, Aerial maps are great to find thick cover and food sources (corn fields),Topo Maps are great for finding fingers, funnels, and saddles and then....

Scout the land, and look for signs. Then.....

Trail Cameras, I dont know if there is a forumla for Cameras per acre. But I would start with 2, then move up from there.

Once you know where the deer activity is at then you can think about planting food plots, mineral blocks, and feeders.