I'm not a fan of a place that will book you same day. Also avoid sketchy looking places, if you're looking for a reputable massage, not sex work. Also red flags are someone who doesn't listen to your concerns, someone who promises they can fix everything, and (for me) a generic place where they won't tailor things to your needs. As far as benefits go, there can be a benefit from going a single time! Depends what you're looking for. If you have ongoing issues that's your like to work on, regular massage is great!
Finding the right massage therapist is like finding the right therapist (if you haven't done that either, there's a bit of a feeling things out process to find someone you really connect with and can do some good work with).