I've done it 7 times, riding it 6 and traveling with the camp crew once (2 weeks after I was hit by a car; no way I was getting on a bike with broken ribs). It's an amazing event and far more than just a ride. Far more than just a ride with great services, signage, food, showers and entertainment. CO was founded and never strayed from its mission to bring awareness, business and improvements to the struggling rural communities its founder was seeing and reporting on as the up-state reporter for Portland's big newspaper. The towns we travel through love us, unlike any other ride I have ever done.
A couple of tricks that will make life easier: Get a really big bag. REI carries huge sailor style duffle bags (almost certainly spurred on by CO demand). Adhere to the 60 (or is it 65?) pound bag limit. High school kids will be loading it into the trucks. Pack it so nothing can get damaged. Mark your bag at each end with distinctive tape. Note the truck it got loaded into. (There will be three trucks with color designations. At the next days camp, each truck will unload the bags into 3 lines, 2 to 3 bags deep with just the bag ends showing. There will be 20 bags looking like yours on your truck.) If you are porta tent camping, ie if you rented a tent, skip the above re: the baggage trucks.
Bring clothesline and clothespins. Some laundry soap. (Don't count on more than a bucket and cold water for wash.) Bring 4 pairs of good shorts and a fifth. (Laundry isn't always possible on the schedule you plan. By day five, this ride starts becoming a little like family. The usual levels of "proper" matter far less. After 4 days of maybe hard riding, clean shorts matter far more.
The blue rooms (porta potties): CO provides over 100 and their crew does an amazing job. But there will be lines and messy ones. All CO vets know - you use the facilities any time they are free. Whether you need to doesn't matter. (When the line is around the block you will be very glad you did!)
Bring a towel, keep it as clean and dry as you can. Towels for rent are provided as a service by the local communities. They may sell out before you get there. The community might number 12 inhabitants. There might be no community at all.
There's lots more. Watch others, ask, listen.
Ride the options. Far fewer riders. (Well, I'm guessing a lot will do the rest day up and around Crater Lake. After all, isn't that the point?) The options are often amazing roads and places. (This year most of the non-rest day options are gravel. That is new. I'm going to bring 35c tires and throw them on for those 3 days.)
Most days, it is not hard to to arrange to ride with or without others. I do both depending on how I feel. I've gotten to ride alone in amazing country many times. (Did a 16 mile descent without ever seeing another rider.)
When you see a guy with an orange-bronze old/classic Peter Mooney fix gear, come up and say hi. Or ask at the Rider Services trailer for Ben the fix gear guy. (Maggie, the woman with a pink wig will know exactly who you are talking about.)
Come ready to enjoy it all!
Ben