The first baseman positions himself to the right of the first-base bag and toward the back of the infield dirt when no runner occupies first base or on the first-base bag after a batter reaches first base.
On defense: The first baseman is responsible not only for fielding ground balls hit in his vicinity but also for catching throws from other infielders to force a runner out at first base. The first baseman often has to "scoop" one-hop throws from an infielder or pick low throws out of the dirt.
On offense: Since first basemen don't require the range and quickness seen at other positions on the field, they tend to come with high expectations on the offensive side of the ball. Generally speaking, first basemen rank well on baseball's home run and RBI leaderboards.