NFHS has a PDF file at
http://www.nfhs.org/staticcontent/pd...rerstimers.pdf
Also - Keep your eye on the ref for re-starting the clock. Don't forget to change the arrow at the start of each period. Double check with the scorebook at each timeout - score, team fouls, individual fouls, whose possession coming out, time left and score (in case clock gets unplugged or spazzes out - it happens). If you have to keep track of individual scoring, it helps if you and the book have a spotter.