A pointer I can give that I have been doing and I have also seen in print is to practice at longer ranges...40, or 50 yards or more but limit your hunting shots to 30 yards or so. After practicing at the longer ranges 30 yards will then seem like a piece of cake.
As far as using a rangefinder like DeanoZ had indicated that its good to use once your in the stand to determine distances to trees etc.. were you may have a shot opportunity before a deer actually comes in.

