Bb instruments are transposing a major second down (and + or -1 octaves or 2)
Eb instruments are transposing a minor 3rd up or a major 6th down)
F Horns are transposing a 4th up (respectively a 5th down)
To write the voices for transposing instruments you have transpose the notation of their voices by the same amount - of the intervals of their transposition - in the opposite direction (up or down).
Bb (transposing 1 major second down)
Transposing instruments -> notation
Bb (major 2nd down) -> major 2nd up
Eb (minor 3rd up) -> major 3rd down
examples: Bb trumpet plays C -> sound = Bb
but writing D -> trumpet reads D -> plays D -> sound = C
Eb Horn plays C -> Eb
however notation A -> horn reads -> sound = C
The key and signatures are also the same amount of the interval in the opposite direction of C:
Bb-instruments have 2 # more than concert picht (respectively 2 naturals less)
Eb-instruments have 3 # more than concert pitch and 1 sharp more than Bb instruments.
Mind that some musicians with transposing instruments read and play concert pitch in G or F clef by transposing themselves. You have to know what your musicians are reading, e.g. tenor and bass instruments as Euphonium or Trombones.