Since there seems to lack any information for what to do at Ingress events / anomalies. I present my version, in hopes to help you.
How to prepare for an Ingress Anomaly.
Bring a battery / power-brick
No matter your phone. I doubt it'll be able to run Ingress and other team related apps for four hours straight. Clusters run back to back, so you won't have time to run home and charge. Plan ahead, bring a mechanism to charge.
These events use supplies and that is no stretch of imagination. I'd expect to use in the range of 800 - 1400 items.
Have lots of Power Cubes
Without XM, you are useless. You might as well have a dead battery. You can't deploy or fire without XM, and even scoring the cube here and there off hacks will only give you another 30 or so seconds.
Go in with a team
There are people who start planning from the instant they know the event is coming. There is nothing worst than thwarting a massive team effort unintentionally, because you didn't know something. Find your team when you arrive for instruction or get involved early to make sure this doesn't happen.
Keep it clean
At the end of the day, this is a game which is suppose to be fun. Don't do something you'd regret. There is no need to sabotage bikes or injure the other team. Keep it cool.
Play as a team-mate
Going rogue in an event is tough. The splash damage in any cluster from 100+ people will destroy everything within 150 meters. You will have zero luck going rogue. Don't do it.
Understand the scoring
While these are different for each event. The general time more points are awarded for volatile portals and for a field covering the cluster, and a small amount of points for non-volatile portals. Since each anomaly scoring is different in every way shape and form, this would be best to confirm with your event/team lead.
Use supplies in a smart way
The only important parts (score wise) of the event are the measurements which occur in each cluster. This is when a "snapshot" of the area, portals and fields are calculated. Thankfully you know the "
5 10 minutes" this measurement will take place. This is when you will be deploying / firing non-stop. Outside of that time, refrain from using large amount of supplies.
Don't multitask during a measurement window
If you are in a
5 10 minute measurement window, the worst thing you can do is leave Ingress. You have no idea when the measurement is coming. Save the notifications for afterwards. Every agent is needed for every measurement window.
Play to your abilities
If you don't have the supplies to withstand a constant deploy/fire L8 race at a portal. Take your efforts to where they will count. Find non-volatile portals away from the action and link / field. (Assuming there is no huge field being made and that you aren't interfering with another portion of your team).
Understand a volatile showdown
What happens when you get to a volatile portal and 40 other people are standing around it? The measurement window opens at the top of the hour, usually. Its an all out fire / deploy from both sides. Defending is easier, since you just have to mash the deploy button. As an attacker, remember to always have agents trying to deploy as well as attacking. For a split millisecond, it may be a neutral portal, and that's all you need to claim it and switch to defending.
If you are individually browsing Google Plus during the event to identify the volatile portals, then you are making a mistake. Get someone who can't attend physically to do that for you.
Understand the location(s)
The instant one cluster ends, the next one is under way. Thankfully you have 30-45 minutes till the volatile portals are announced for that cluster, but you still need to relocate to that cluster. Sometimes they will be in walking distance. Sometimes not. Get an understanding prior to the event how you will travel among the clusters.
Update: The way volatile portals are announced have changed over the anomalies. One way to detect them now, involves looking for the ornament on the portal (shown below). Other methods for primary sites involve decoding materials and/or utilizing the common Ingress social media profiles.
So if you see a portal with that triple hexagon border, that is a volatile portal.
If you are planing to come to an event. Today is the day to begin planning. Find the Google Plus groups, start farming / keeping supplies. An organized agent is a smart agent.
For a more in depth (with real life examples and pictures) check this blog post.