Overview
In space a body in motion stays in motion. To prevent that your flight assist will control your thrusters for you. This has the negative effect of slowing your maneuverability. It's important for every pilot to know how to fly using both flight assist on and off (abbreviated to "FAO" from now on).
Tethering
Tethering is when you fix the nose of your ship to a point in space. This can be a star, an asteroid, or anything you like. This will keep you from drifting in an undesired direction as well as control your velocity.
Boost Bleeding
Boost bleeding is done by activating your directional thrusters at the same time as your boosters. By holding down the directional thrusters, a majority of your speed is diverted from the main thrusters. You can also perform a braking maneuver by opening your cargo hold and/or landing gear.
FA Off Turning
Also called circle strafing; you will turn faster than simply pitching or yawing. Pick a direction you want to turn and use the opposite directional thruster while in flight assist off mode. For example if you want to pitch upward, you would activate your down thrusters at the same time.