Fiance Visa

I'm looking for some help advice on a fiance visa.
My fiance is a UK citizen and we've been engaged for about 6 months (at time of writing this). I've been hoping that somebody can share their experience or help with suggestions on the best forms of 'proof' documents.

We've known each other for a year, we've met via Facebook. He came out in July last year for a week and I spent 6 months out there already.

Am planning on going out to visit again (not in a rush to do fiance visa) but when I return I would like to get it started.

P.S.
Instead of making a new thread for a simple question, I'll just ask here.
I know that I was in for 6 months, so I must stay out for 6 months. So does that count from the day I left the UK ? Just trying to figure out when I can go back if it helps [Left Feb 21,2009]