Don’t look down. Don’t mess around with your watch as your cross the finish line. Don’t obscure your bib number. Don’t drag your feet. Don’t make the “shoot me, shoot me now” face. Don’t whack others runners with wild arms. Don’t, whatever you do, don’t cross the finish line with a cartwheel or by walking on your hands– your shoe chip which is tracking your time might not connect with the finish line sensor!
Do run directly under the clock. Do try to move into an empty space so you get photographed solo (unless you’re crossing the finish line with another person intentionally, of course). Do lift your head and arms, either all the way up or out, or with bent elbows at shoulder level. Do make sure your bib number is visible. Do stride strong. Do smile, and do take a moment and feel proud for finishing– that sort of thing shows.