Animals require salt and minerals in their diets, and will seek out the foods that naturally provide those needs. Salt and mineral blocks set out for domestic livestock commonly attract deer. A salt block can be purchased from a feed supply store and set out specifically to attract deer. The salt needs to be placed in an area frequented by deer and left in place without moving it until the deer find it, which can take anywhere from hours to days. Once deer have found the salt block, they will continue to return to it.
Locate an area frequented by deer. Place the salt block on the ground where deer tracks and droppings evidence their passing.
Place the block in an open area surrounded by brush or trees, where the person watching can hide without being detected by the deer.
Drive a steel "T" post into the ground if the ground is we,t or to keep the block above snow. The block has a hole drilled into one end; mount the block by dropping the hole end over the top of the post. Adjust the height of the post so the block is 3 feet above the ground, or above the snow level.
Replace the block when it is worn and melted down to a small piece.
TL;DR (Too Long; Didn't Read)
Deer are wary when they come to a salt block, as they know predators could be waiting for them. It will take time for the deer to come out in the open to use the block. Watch patiently from cover until the deer come out. Wear camouflaged clothing to help hide your presence. Deer will detect any sudden movement, so be still when watching the deer.
Many states do not allow deer hunting over a bait or salt block. Check game regulations before hunting over a salt block.