This site was helpful for my first double last year:

http://www.lisbonne.com/davisdouble.shtml

I would also suggest trying to find ride reports for the doubles you are planning to do. That really helped me in my first year of doing doubles - knowing what to expect. A couple of great folks who do ride reports on CA doubles are:

http://felixwong.com/news/category/b...ble-centuries/

http://www.adampaul.com/cycling/reports.shtml

This may help Fredwina - I think you're aiming for CTC?

KG - I would caution trying to ride at someone else's pace on a double unless you are also training comfortably at that pace. It is great to have the benefit of the draft, but not if you are blowing everything to stay with someone else. I've done it both ways - on my own and with others. The on my own ones were actually some of the most special - there's something about just being alone for 200 miles (give or take hooking up occasionally with others). It really makes you mentally tough. (Of course the 600k was a whole different mental story!!)