First, study the course map and any spectator information available from the race so that you can find a good spot, or spots. The Marine Corps Marathon had a lot of information on their website for spectators and it was definitely appreciated. The website identified multiple good spots for spectating and we picked one on the national mall between mile 17 and mile 18. There were a lot of fun spectating here and it was cool chatting with people. We also happened to be right next to a group of people giving out free beer and they were a fun group :) It was funny to see runners run past, realize that there was free beer, and turn back to get some!
Also, go early. We knew that none of the people we were watching for were going to be front runners but it was still really interesting to see the front of the pack speed by. We were walking up as the wheel chair leaders zoomed by and we were in place with the camera out by the time the front runner ran by. Here are some photos of the lead runners
And here was the first woman we saw go by
Take a fun sign and a noisemaker of some sort. We had a sign and it seemed to really perk up some of the runners :) A couple of them flashed the 2 Legit sign at us as they ran back. Some of them yelled out and one even stopped and asked that we take her photo with the sign with her phone. We did not take anything to make noise with other than our voices or hands but a cow bell would have been much appreciated by the end!
Another great way to interact with runners is to call out their names. A lot of the runners had their name or some sort of identifying mark on their shirts. By mile 17 some of them were too far lost in a fog to hear us but the ones that heard us really seemed to appreciate it. No one seemed to care that we didn't actually know them. And some of them had fun costumes that we yelled out for too.
Also, really look at the people and the faces that go by you. You could tell that everyone had their own story and their own struggles that they were overcoming on this day. And the people running with flags or pushing people in wheelchairs were especially inspiring.
Lastly, if you're looking for someone specific, sign up for runner tracking. It was really crowded toward the middle and end of the pack and it was hard to pick out a specific person. In fact, we missed seeing one of our friends in spite of having runner tracking and in spite of knowing what she was wearing!
You can see how crowded it was and how many runners there were at this point
And if you're into photography, take your camera and a fast lens! The race was a great opportunity to practice taking photos. I have a bunch but here a couple more that I really like.