When I really want to listen closely and for a while, I have a pretty obsessive dietary and physical regimen:
1. No caffeine or alcohol during the days that precede the listening session: usually impairs hearing.
2. No red meat on the day of the session: usually, a small portion of sushi is best.
3. A long, hot bathe: actually, I think the body listens through the pores as much as the ears.
4. Perhaps, a nap, if tired.
5. No long car or train rides the day of the session, or anything involving alot of vibrations.
6. No audio magazines in the listening area when the session approaches.
7. Freshly ventilated and dusted room.
8. Perhaps some light yoga beforehand.
All of this while all of the components in the system are warming up: hopefully for three or more days beforehand.