Whais is DSSSM
D - Doors
Check it is clear before you open your door and make sure the door is shut properly when you get in before starting a journey. Be careful on a windy day when opening your door as it can easily fly open with the force of the wind.
S - Seat position for pedals
Slide your seat to enable you to reach the foot pedals, making sure you can press the clutch pedal all the way down with your left foot. To ensure you can maintain control of the car, drive wearing sensible footwear. Seat will slide back and forward. Make sure it locks into place (you can sometimes raise seat if needed).
Seat adjustment
Alter seat if needed to enable you to reach steering wheel, adjust your rake (angle of seat) for comfort.
The head restraint should be adjusted so the rigid part of the head restraint is at least at eye level or top of the ears and as close to the back of the head as is comfortable. (Some restraints might not be adjustable).
S - Seatbelt
Wearing your seatbelt is a legal requirement and will protect you in an accident (make sure there are no twists and all passengers wear theirs). The driver is also legally responsible for passengers under 14 years old.
M - Mirrors
Finally, once in position, adjust your interior mirror and your door mirrors to give you the best view to the rear and sides.
Adjust your interior mirror by using the outer rim (to avoid fingerprints on mirror) to give the best view directly behind, in slight favour of the driver's side.
Adjust your left and right (exterior) hand mirrors to enable you to see from the rear and sides - you should have part of the side of your car in view.