(1) Dress warmly- As it's going to be cold and rainy (see forecast on right), put on 1/2 to 2 1/2 extra layers of clothing --- particularly covering well your head, hands, and toes. Also, manage your potty needs as the port-a-johns are not heated. If the wind picks up, stand behind tall people.
(2) Crowd Control - It's nice to be spectating in a crowd because it's loud, fun, and warm, and "cheer zones" near a clock lets you know what time and what mile the race is at. But here's a disadvantage: unless you're James Earl Jones, runners probably can't tell which voice is whose from a cheering crowd. For me, even if I react in time and look over, I might have trouble identifying you in a crowd in time. So, my suggestion is to split from other spectators when you are expecting your special someone to pass through or wear something outrageously bright so that we can spot you. Also, secure your valuables and don't trip.
(3) Cheer Endurance - If you have a noisemaker, bring it. If you're like me and cheer for everyone that passes by, you will not have vocal cords for work the next day.
(4) Yelling Stuff - I know how you feel... you have a few seconds to yell something coherent to the runners passing by, and when they look like they're suffering, it's hard to figure out what words actually help in that short window of time. And then cheering quickly gets boring because you're yelling the same two phrases to everybody for the last hour. Or if you brought a sign, you worry that I'd trip and sprain my ankle while trying to read it. (This last worry is mine only.)
So, what stuff to yell? Here's one runner's perspective. In a marathon in which I am tired or bored, I love hearing something funny, such as don't try to win! want this chair? keep moving! I also don't mind constructive advice, like relax your stride! or turnover! If I'm immersed in conversation with a cute runner or am among a pack, something quick and easy like Go Helen! (use one of my names) will get my attention. Something hopeful is also good: There's hot soup and tea at the finish! Or something angry usually gets me to run faster, like Rick Santorum is beating you!
I would say stay away from screaming: 10 miles to go! You're almost there! Pick it up! And no riddles/puzzles that I can't solve.
Thanks to all who are coming out tomorrow!