You should expect the petition to be approved on the US side within 6 months of receiving the receipt notice (NOA1). If after 6 months you havent yet been approved, then is the time to start making phone calls. Anything before then, and you are within the average processing times.
Once it has been approved, the petition will then be sent to NVC. Expect it to be here for around 3 weeks. Could be longer though or could be less.
From this point it is sent to the interviewing consulate. The consulate will then send your fiance packet 3 which will include the interview checklist, medical info etc. Expect about a month to receive this once the consulate has the petition (again, could be longer, could could be less).
Once the consulate has the check list sent back to them, an interview letter will be sent to your fiance. The interview could be anywhere between week and months of the sent date. My interview was scheduled for one month ahead of the date the interview letter was sent to me....though in extreme cases, Ive seen peoples interviews scheduled 11 months ahead of the letter (this was a case in PI).
Once the interview is over and the K1 is approved, expect about a week or so to get the visa in hand. India could be different though and issue the visas on the same, but from my UK experience, the visa is couriered to you (the embassy keep our passport after the interview to process your visa).
My personal experience from start to finish was around 9 months which is VERY average.