It's probably too late to join up with Arctica - it's kind of a coveted volunteer opportunity, and kind of late in the season.
Don't sign up for anything you think you might flake on. If you think you might do 2 out of 3, look for walk-up opportunities. Black Rock City has lots of places where you can help. You'll still be third tier (by your rules), but doing more matters.
Put lamplighters on your list - it's a great walk-up opportunity, which means you can go and do it on the day.
Put the BRC Post Office on your list - another great walk-up opportunity. Deliver mail and packages to camps, meet a lot of fun people along the way.…lots of other stuff, there's even a job placement thing over at playa info if I remember correctly…
Work a shift at the Idea Deli (my camp), basically sharing good ideas, bad ideas, any kind of ideas with random people. Show up on the day (we're on 8:30 at Esplanade) or PM me with your email addy if you'd like to 'sign up for a shift.'
If you do want to be proactive enough to sign up and stick to a scheduled shift, I think Greeters is still looking for help, as is Playa Info (big influx of newbies means we'll probably have a big influx of people looking for help). If you want to be hardcore, I'd say take a look at Gate, Perimeter, and Exodus
. Want to help make getting into Burning Man go more quickly and more smoothly for everyone… GPE is the way you do that.