I think this is among the best answers - getting to know your future boss and coworkers ahead of time is the best way of figuring whether you like these people

I think this is among the best answers - getting to know your future boss and coworkers ahead of time is the best way of figuring whether you like these people or not, probably the single most important determiner of your happiness at that job. A good boss knows how important this is and should be equally cautious in bringing you on. If not, a big red flag that you're being brought into a potential sweatshop/sausage factory. A lot of this starts from how you found the position in the first place, and why I believe it's generally better to job hunt at tech meetups and conferences - before you've been thrown into the formalized process of interviewing, you've met these people already in a more natural environment.