Actually that depends on the size of the vessel, and the current weather conditions level.
Bow and/or Stern thrusters are mini propellers built into the ship, which face port and starboard (270 and 90 degrees). They assist all types of ships in carrying out complex manoeuvres, but are mainly used to help dock the ship. Having them fitted to a ship enables that vessel to turn in it's own length when stopped or at very low speeds.