Pick a windy day, feilds that have been sprayed are easier to stalk in, but deer do not tend to bed in them as well if there isn't some weeds as well.

This year I got within 15 ft of a Spike. I was gun hunting actually, and heading to my stand. I passed the little buck up, but is was comical how close I got. If the terrain is rolling, you can sometimes see a deer feeding, or even bedded from a distance, then count the rows over (3-6 down wind) and plan your stalk. In the case of the little buck this year, I saw him at 150 yds, and got within 15 ft. Even when I tried to spook him out of my way by clearing my throat, he wouldn't leave, and could not pinpoint where I was (he was right in front of the stand I was planning on hunting).