I've met a few cabin mates from this site, and some of my advice would be to:
1. Communicate fully. There are many different personalities out there.
Do you expect a 7 day date? A dinner companion? An activites/excursion partner? Let's face it, most things are more fun if you "know" someone, but if you are outgoing and personable, there will be a pool of 3K +- people that would possibly be activities partners.
My last 2 cruises with a new cabin mate was great! We did a few excursion together, as well as separate, and did some meals together. She met new friends, as did I, and would enjoy cruising with her again.
And to be as tactful as I can be here in digital form, I've not gotten physical with any of my new cabinmates except one whom told me she was my girlfriend at the time, nor would that be of concern to me.
2. Be forgiving
If you have pet peeves, mention those in the beginning of the getting to know each other stage, this is will defer the possible "OMG, you put pepper on your cottage cheese?! My cruise is RUINED!!"
3. Be polite, yet not run over
It's really a give and take. Simply state firmly what annoys you, what you personally like, etc. I've not many annoyances, and my cabinmates have had few complaints
With so many point systems out there now, many will want to take advantage of them if they can, be forewarned that the points won't matter if your cabinmate doesn't pay, so I would suggest each paying through the Cruise line (they're used to it)
Just my bit...