Anytime when im scouting and see deer, i will try to remain unseen until they leave and i f i like the general area i will generally try to set up on their trail where i see the most use or if their are faint trails intersecting i will try to set up about 25 yards away from those, since typically they are going to be from a buck, if rub line is nearby or a primary scrape area, that makes me feel even better.
But it really depends on what part of the year it is
Early season and late season- I will focus mainly on food sources and the trails that lead to and from them, oaks, corn, beans, whatever is nearby. Oaks have been great for sightings in the early season and corn an beans have been magnets for late season sightings.
Mid season- Bedding area's or staging areas for food sources or hidden wood lot food sources
Rut, in the past i have tried to be by rubs or scrapes, but i have had minimal luck during the rut other than my first buck kill in 2005, this year i will be focusing on family bedding areas and setting up downwind of them
It all depends and where im at, what time of the year it is and what and where food/water is comes in to play as well.
Them Darned ol' deer.