In these videos, Shawn Royster talks about the purpose of down-the-line and cross-court passing shots.
Many players error by trying to hit passing shots too hard or too low (like a kill shot). It is much more important to hit a passing shot accurately. This will force your opponent out of center court position. To gain center court position, use a passing shot. Do not hit your passing shots so hard that they rebound off the back wall.