Parallel to brushing the teeth on the outside in circular motion, the inside of the teeth are cleaned with the Red-To-White technique, then later the technique is also used for the outside. The Red-to-White technique is named for it's movement from the red gum towards the white teeth.
Place the toothbrush in a 45° angle on the gap between gum and teeth and moved it down over the teeth, typical in a rotating motion of the wrist. With this motion you want to scrape and throw plaque of the teeth.
For the inside of the center teeth the movement is a bit easier and more fun. The brush it used vertically and dragged from the gum over the teeth. It can leave some sprinkles on the mirror or the wall, take this as a proof of the brushing been done right.