As a fairly regular traveller

- drink little or no alcohol

- if flying west, stay up to a normal bedtime

- if east, don’t sleep in

I usually end up breaking qt least one of these, but they do work and imo are basically all you need

Do you do anything on the flight itself (other than avoid alcohol)?

The one I forgot is drink as much water as possible.

Usually I try and work a bit, and will listen to music and relax with my eyes closed (I can’t usually sleep much unless in business class which is not common)