Nouns

(n)lookout, sentinel, sentry, watch, spotter, scout, picketa person employed to keep watch for some anticipated event
(n)scout, talent scoutsomeone employed to discover and recruit talented persons (especially in the worlds of entertainment or sports)
(n)scout, pathfinder, guidesomeone who can find paths through unexplored territory

Verbs

(v)scout, reconnoiter, reconnoitreexplore, often with the goal of finding something or somebody