Trust starts when someone tells you something small and true and you don’t make it weird.

Openness gets tested in miniature first. Somebody mentions they are nervous about the test, or that they still sleep with a light on, and they watch what you do with it. No reaction is the reaction they are hoping for: no teasing, no repeating it, no sudden intensity. Pass that and the next thing they tell you is slightly bigger. Flinch, and the door closes without either of you discussing it.

Practice receiving things plainly: when a friend says something true, say something ordinary back and let the subject move on. Most of the time, not making it a moment is the whole job.