I see ping pong tables and free beer as a red flag of sorts and seek workplace that is more formal. The idea is that the less it attempts to be personal/cool/cultural the less personal things (e.g. gender or peoples attitudes/biases or who-likes-who) matters and the more actual work matters. I have no stats to support this, just my guess and some experience.
I also try to find what exactly am I going to do, whether there are clear responsibilities etc. It is easier to prove what you can do if responsibilities are clear and if you can work autonomously so your work is clearly your work. (I don't like true agile partly because then too much depends on impressions and politics and assumptions.) Moreover, clear responsibilities mean people have harder time to act on "women are not technical" assumption. Plus, fluid team structure pretty much guarantees a random collegue will try to micromanage me (like when they have ambition to be leader they tend to think I am good place to start) - then I had to fight for having normal work. Although I am usually able to get rid of that collegue, it is way more pleasant when I dont have to go through it.
On interviews: if it is technically and business oriented, then it is good flag. If they are too cool or personal or seem to be reacting to my gender (includes also being more friendly then I would expect on interview) then it is bad flag.