It depends on belt as well as the teacher. Most schools you need to know(or at least should) one step sparring for your current belt as well as your former belts, hyungs(forms) for your current belt as well as former belts, certain kicking, striking, and blocking techniques and certain self defense moves. depending on teacher you might need to know certain korean words or phrases. also depending on rank you might need to do free sparing and board breaking and advanced 1,2,3 step sparring. You might be asked to do things from your previous belt so you need to know everything you have been taught to up to the point you are at. There are a certain amount of points you need to pass each test, i believe it is 130 for white and it goes up from there, to 250 for black. each thing you are asked to test on is a certain amount of points. If you are a black belt they will(or should) time your forms. The first degree black belt form must be within 2min. 5sec. and 2min. and 25sec. to pass. every form has a time. that is not really too important until you get up higher in rank. Yes you must start at white, ocassionally the teacher might skip you up belts if you have prior martial arts experience, but you must learn all of the tkd things you need to know before moving up. the belt system may vary slightly from school to school but for the most part it is white, orange, yellow, camoflauge, green, purple, blue, brown, red, recommded black, black.