The thank-you note that is not a formality.
One short message that adds something to the conversation you already had — and a second, shorter one if nobody answers.
What did you talk about, and what did they say happens next?
The two-sentence thank-you that works
Reference one specific thing from the conversation and answer one thing you did not answer well.
Following up when they go quiet
The second message, the third, and the rule for stopping.
After a panel interview
Who to write to, whether to write to all of them, and what to send the recruiter.
Questions people ask first
How soon?
Same day is ideal; within 24 hours is normal; after three days send the follow-up instead.
Should I send it to everyone I met?
One message to the person who owns the decision, and a shorter one to the recruiter.