Recently gone through this - I got married just over 3 weeks ago and DW had visa approved earlier this week and arrives here tomorrow! YEH!
Biometrics - you print off the booking confirmation and take that with you, it has a barcode on it. At the appointment they will stamp this sheet and sign it - that is the receipt that you send.
As to what we sent
Cover letter signed by wife just briefly outlining what we were appying for and what was contained.
Printed application
Wifes passport
Marriage certificate
Notorised copy of my passport (just the photo page) - cost me £30 from a local solicitor.
Letter of intent from me - I'll post on here a copy of what I put if you wish
Letter from employer (my manager) detailing my employment, salary etc
3 months salary slips
3 months bank statements - these were just printed from online banking
Print outs from my online savings accounts and ISA's etc.
Mortgage statement from this year
My birth certificate - not sure if that was required or not
Travel itineries from when we'd visited - couldn't find one for one trip but did have the boarding pass stub so included that.
3 photos of the 2 of us together
Biometric receipt
I think that was it
There's a checklist on the BRITINUS website (I think) and thats basically what we sent.
Wow! I feel like an "expert" now, after months of looking on here, asking the questions, reading every post like this I could find....we finally made it!
Again - thanks to Vicky and everyone else on here for their help and advice, whether directly or just what I found on other posts - this site really has been invaluable.