You cannot forget to untap your permanents on the battlefield at the start of each of your turns. If you move on to the upkeep step, or even draw step, you need to go back and untap all the necessary permanents. If you are playing quickly and draw before untapping everything you control, thats generally fine as long as you end up with a legal result, are not gaining an advantage in some way and neither player is confused. In tournament play you are not penalized by having these permanents remain tapped for a bit, however you may be asked to play a bit more clearly.