The Lander's main thruster (or twin thrusters) is always on the bottom of the Lander. It is your only means of getting about and it is the only rocket on your ship that uses fuel. Clicking the mouse button 1 activates it until you release the button. The main thruster can be continuously turned on and off, it can be turned on and off as fast as you can click the mouse, and when it comes on it is instantly at full throttle.
Using the mouse the main thruster is binary, meaning it's either full on or full off, there is no inbetween throttle setting. So to hover in one place you have to continually PULSE the thruster on/off, you will bob up and down much like a bird hovering by flapping it's wings.
Because you have only one means of thrust, you must use this thrust to both accelerate your lander, and deaccelerate. This can make it quite hard for someone used to driving a car, where you use a seperate accelerator and brake. In lander you angle your craft forward and use your main thruster, this will make you accelerate forward. Then if you want to stop you angle your lander backwards and use your main thruster. Simply speaking it will take you the same amount of time to stop as it took for you to accelerate. Because of this it can be quite strange playing lander when you are used to driving a car, because a car can stop a lot faster than it accelerates, but a lander cannot.
When going in any direction, you need to remember that the angle you tilt your lander can't be too excessive, because some of the thrusting power still has to be used against gravity or you'll crash. It depends on the gravity of the planet, and your thrusting power.
when traveling in lander, you will eventually want to go as fast as possible. This is safest done outside where you can fly forever in any direction. You plant your finger down on mouse button 1, angle your craft forward a bit and hangon. You'll need to finetune your pitch so that you don't go too high or low, but stay straight. You'll soon reach terminal velocity where you won't be able to accelerate any further.
Using the default controls of Mouse and Keyboard is the way i play lander. The mouse controls your rotation around the Z (roll) and Y (pitch) axis, while the C and V keys on the keyboard control the rotation around the X (yaw) axis. All of these are ROTATIONS, ie: you're not actually moving anywhere, just rotating on the spot. Rotation can also be called ATTITUDE.
In reality what is happening is that the mouse controls DIRECTLY the roll and pitch of the Attitude Leveler HUD in the bottom right corner of your view. This direct control is of the GREEN level, the RED wireframe level is your craft's actual currently positioning. You will notice it can take some time for the RED level to catch up with the Green level, this depends on the power of your engine's attitude thrusters, they can only thrust so much.
Also in reality the C and V keys on the keyboard actually control your VIEW. They rotate your view to the left and right, and the lander follows the rotation via the Attitude leveler HUD. No matter what Lander or Engine upgrade you purchase, you will NEVER be able to make the view - and therefore the lander's yawing - rotate any faster left and right. Since the mouse is an analog control, and the keyboard digital, i guess they had to set a constant speed for yawing since a digital input signal is only on/off, there is no way to tell the computer to yaw fast or slow. A good way would be to use a control mechanism that has 3 or more axis instead of the mouse's 2.
If you are touching a surface, you will see a light on your Velocity HUD and the Lander's attitude thrusters will automatically disengage unless you are firing your main thruster. This effectively makes it so that you cannot rotate your craft while it is landed. You will notice however that you can still rotate your view with the C and V keys, and that every movement you do is followed with the green level on the Attitude Leveler HUD.
The W key will automatically reset the Green level on the Attitude Leveler HUD to the horizon. Therefore if you are in the air the Lander will straighten up, and since the horizon is all around you, the lander's YAW will not be effected. If you are touching a surface, holding the W key will activate your otherwise inactive attitude thrusters and your lander will flip itself to align with the horizon. You can hold the W key for as long as you want, because the attitude thrusters don't drain your fuel.