I've got an event 104 mile "ride" this Saturday with 3800 feet of climbing at 94 degrees. Here is what I've found doing several of these types of rides.
1. Don't start out too fast by yourself. Everyone is excited and they usually take off fast, find someone to draft off of, and look for groups to form.
2. Know the course before so you know where the hills are. Download the map if you can onto your GPS unit.
3. Draft as much as possible and be courteous by pointing out obstacles in the road and turns.
4. Bring your own food and don't eat anything new. I've seen riders get sick because they introduce something new to their stomachs.
5. If you're in a group, and it is going too fast, drop off and see if you can catch another group. I was in a group and I was drafting, doing 400 watts @ 30mph on the flats, which definitely was not sustainable.
6. Put your food in plastic bags for each stop and mark them 1,2,3..etc. I've seen riders who are fumbling around for drinks, powders, bars, etc. Put it all in an individual bag and save time.
7. Don't leave stops by yourself. If you're by yourself, wait for a group to leave and hook on.
8. Go to the bathroom every chance you get. You never know what the bathroom situation will be like at the next stop.
9. If someone is drafting off of you, be polite, pull them for a while, flick your elbow pull out, and then draft off of them...
10. Have fun, it's not a race, it's a ride.
Oh yea, don't forget to start your Garmin/Wahoo GPS computer at the start like I always forget to do on most big rides.