For the perfect sitting posture, the following should be followed:
(a) Use cushioned chair that helps you keep your body straight. The chair so selected should be adjustable, so that you can set the height of the chair to rest your feet flat on the floor. Keep your feet on the floor or on a footrest.. Some people like sitting in a slightly lounged position as it creates less stress on the back.
(b) Support your lower back.
(c) In typing-mode, never cross legs. Maintain a distance of 15 cm between the two feet.
(d) Both the feet should be placed on the floor maintaining a distance of about 15cm between the two feet.
(e) Have a comfortable chair with adjustable armrests, if possible.
(f) Have a cushioned seat.
(g) Your keyboard should be at a height that allows your elbows to be bent and close to your sides.
