The X Drill focuses on giving pin hitters multiple opportunities to hit inside sets. At Oregon State, they usually run it with a "2" set.
To start the drill, form a line of hitters on both the left front and right front. Have someone set or toss a "2" from the middle of the net. The first ball will be hit by a player from the left front line. The second ball will be hit by a player from the right front line.
From a top view, this drill forms an "X," which is how it go its name.
Go through 2 times on each side focusing on hitting angle, then go through 2 more times on each side focusing on turning the ball back to the line.