It is quite routine. There was a 30 min phone interview, followed by an one-day onsite interview including an one hour presentation and 30min personal interview for the whole day. After a few days, I was made an offer and I accepted it. Then I believe I have to go though background check. There is a mandatory health clearance requirement.

The interview was like any other postdoctoral interview: you give a seminar on your previous work, then meet the people of the lab and the PI. You discuss the project you would be working on, potential starting date, etc. Depending on the PI, you will discuss your career plans, which he/she may not agree with (for most PIs in the Harvard community, the only way to go is academia; industry or non-bench careers are, according to them, for losers...). You can get the offer at the end of your interview or it may come later. I never get the chance to negotiate salary or benefits; actually, the PI did not even offer to pay part of the cost of the trip...