Fail to prepare, prepare to fail
This is an ancient saying, but it is also very true. My main tip is to always prepare, and this goes for anything in the working world. Prepare for your day, meeting, and especially your interview.
The time you should take will vary per person, but I spend at least 4 to 5 hours on behavioural interviews. This may sound like a lot, but it’s always better to be over-prepared.