Hi friends. I've taken a lot of help from this site and am grateful. I want to relate my own experience and give something back:

I am a marine engineer from mumbai and had applied for an F1 visa at the Mumbai centre.

Firstly, make sure the OFC and interview dates are separated by atleast 2 days, because you might get tired, travelling daily.

The Mumbai OFC and interview centers are different.

So I have already sailed on ships and possess a C1/D Visa (member of a crew) Visa.

My interview went like a breeze, hardly 2 mins. VO was quite cool and all smiley.

VO was a 'healthy' lady in her 30S.
The interview went like this:
VO: Hi, will you pass me your passport and documents please?
Me: (I had started to say the full salutation, Hi, how are you, I'm good, etc.. But eventually ended up mouthing Hi and passed over the documents.)
VO: So why are you going there?
Me: Ma'am, I'm going to North Carolina State University to...
VO: But what are you going to do there?
Me: I'm going to pursue M.S. in Indstrial Engg.
VO: So did you complete your undergrad in a similar subject? (She might've seen my education details)
Me: Ma'am I completed my undergrad in Marine Engineering.
VO: Oh! (Surprised) Marine Engineering? So why are you making a switch?
Me: Ma'am I've worked as a marine engineer and I wish to pursure a career in logistics and support...(preparing to blah)
VO: So, how many Universities did you apply to?
Me: (Actually had applied to 8, and received all admits, but I said) I applied to 6 universities.
VO: How many admits or rejects did you get?
Me: Ma'am I received all admits.
VO: Oh! (Surprised again) What's your TOEFL score?
Me: 113
VO: That's good! Okay. I see that you already have a C1/D Visa. Have you worked on a ship before?
Me: Yes ma'am, I've worked for 10 months as a Junior Engr and then switched company and worked as a 4th Engr for 8 months.
Who's going to fund your education?
Me: My father is going to sponsor my education.......
VO: What does he do?
Me: He's an accountant with XXXX Ltd. and ma'am my sister will also support me if needed and even I have some funds of my own. (I don't know why I said about my sister and me... I didn't mention my education loan either.)
VO: Your Visa has been approved...blah...

1. They are really in a hurry. So say the most important point first and if they hear what they want to they'll interrupt you directly, sooner or later.
2. Be confident, wear a smile whenever necessary as it helps clear the tension.
3. No salutation is necessary if they ask for documents straight away. Just say HI. Do what the VO does. If he asks how are you, say you're good and ask back.
4. Be there at least 1 hr before. Every minute late is like double the same amount for waiting. The re-verification (Bio-metric) takes up a lot of time.