E.g. clean code, static languages, testing, up to speed with the best practices
Basically where "it works" is not enough and with focus on maintainability
Location: NYC metro area
Check the GitHub repos of people who are on the team. Company code might be private but you can get a sense of who is on the team and how they code. Also see if you can talk to teammates before joining to get a sense of what the day to day is like. There are great engineering teams in the sense of eng practices but horrible culture in terms of management, getting along well with other orgs, etc. So you want to make sure you have both.
Talk to them. It's not going to be clear in the code as it will be with how they talk to co-workers / sort out issues.