The first ninety days as a new supervisor

The most common promotion is from the best technician to the supervisor of technicians, with no training in between. The new supervisor keeps doing the technical work because that is what they are good at, and the supervision happens in whatever time is left. What helps in the first ninety days, in our experience, is a deliberate handover of the technical work to someone else, one regular conversation with each team member, and a manager who is explicit that the job has changed. What did you wish someone had told you, and what did you get wrong?