I use calendar reminders to do them first in the morning. It's important you keep techniques consistent so that you don't fool yourself when measuring progress.

Pushups I do eyes straight ahead chest touching the ground, hand positioning I alternate a bit and push as high as I can. Pull-upps with just slightly bent elbows when down and go as high as I can, hand positioning alternating a bit but keep palms facing me. Don't help with the legs.

Sit-ups neck straight, hands behind neck, knees 90 degrees, elbows and shoulder blades touching the floor and back as straight as possible when down and elbows touching the knees when up. Supermans I just do as high as I can.

Squats I don't go lower than my butt on the knee level to avoid hurting my knees and don't straighten my knees going up either. I keep my hands stretched in front and back straight.

Have fun! It's almost as awesome as Anki.