I did the rank as you go method with some criteria when I first started interviewing. For me, the biggest criteria was training/rotations and vibes. I did consider other areas similar to what
@iheartbacon listed but eventually I threw those out after talking to other people who are in their postdocs now. My reasoning is that it is 1 year. Work / life balance is very important to me but I would rather get a great year of training during my internship and sacrifice an extra 10 hours a week than get a subpar intership that is a strict 40 hours. Everyone I know who did a post doc said it was not as competitive as internship and everyplace was flexible with start dates as internship completions were all over the place on the calendar.
I can honestly say that what I expected to be my top 3 choices prior to interviewing ended up being middle or lower on my final ranking. A lot of that boiled down to my gut feeling / the vibes I got from the interviews and if they had rotations that I really wanted to do. I wanted to find a place that I fit in and the people seemed honest. Several interviews turned me off due to being misleading (aka we love diversity but everyone on the interview / site visit was of one race). If everyone seemed to be super young I was turned off. I don't want to learn from someone who has only been in the field for a year or two. Also, sometimes talking to the current interns, they had fake smiles when asked about their site or the answers were short like they had nothing good to say about it.
Lastly, as you do interviews, if it is not clear, ask how rotations are chosen. Do you choose, does the faculty / training staff choose for you? We were put in a room at the end of our second week with just the interns and we had to put together our rotations with the limits the faculty put on us (how many interns per track in a rotation period). There were pros and cons to this approach but some people definately got the short stick.