It’s better to be sharp than out of tune.
You always have time for the things that are important to you.
Never speak ill of another player; such talk always boomerangs eventually.
For unreasonable conductor requests (e.g. continual demands to play softer), after you reach your limit play exactly the same thing and keep asking “How was it this time?”
Transposition “mental key signature” rule of thumb: – if it’s a sharp key, add a sharp; if it’s a flat key, add a flat. E.g. Horn in G: one sharp for G major, add a sharp = 2 sharps, or D major; Horn in Eb: three flats for Eb, subtract a flat = 2 flats = Bb major).
To transpose horn in A-basso or Ab-basso, simply read it as old notation bass clef and adjust the mental key signature (A: 4#s; Ab: 3bs)
The “13th transposition” is playing a part in C (concert) in bass clef, like reading a trombone part. Be acquainted with it – it will come up sooner or later. Method: read it either 1) in tenor clef or 2) in Eb horn, down an octave.
You can never win an argument with a conductor. On the other hand, there is such a thing as “malicious compliance.”