During a typical practice-noodling-meditation session with my 12-string I will go through a couple of open tunings in addition to standard. I always try to put it away tuned to a lower-than-standard tuning like open G. It's probably not necessary, but it can't hurt. And I'm probably going to want to do some open-tuned stuff first when I pull it out again.
As for capos, I'm currently using one of those over-priced rolling capos that a guy at the music store talked me into buying (I think he was getting a kickback from the manufacturer). It actually works pretty well. It's good points are: 1) It's wide enough to go to the 9th fret of a 12 with no problem. 2) The tension is provided by two springs, one on the bass side and one on the treble, instead of pinching from treble to bass. 3) It's the only capo I've ever found that you can actually leave on at the nut of a guitar with a "dart" (like a D-28) when not in use. On the downside: 1) The springs are pretty strong and one that was allowed to snap back could hurt a finger or a guitar neck. 2) Since it has a roller instead of just a rubber pad, it is more difficult to do a mod to keep the 10th and 12th strings fom buzzing. If you'v never seen one of these things there's a photo at FRETS.COM (Go to the index page and then scroll down to accessories. The photo's on page 2 of the capo section.)