Minor 9th chords
The Minor 9th chord is easy to learn if you are familiar with the 9th Chord. The differences are that one note are lowered and you don't play on the lowest string. If we compare C9 with Cm9 we could see that the notes changes from C, D, E, and Bb to C, D, Eb and Bb.
None for the moment in this category
Notice that the shapes are exactly the same (notice also the irregularity for Bm9 with one extra muted string). This means that the chords for the most part are movable so you can easily find out how to play C#m9 /Dbm9, D#m9 /Ebm9, F#m9 /Gbm9, G#m9 /Abm9 and A#m9 /Bbm9 as well.
Bm9 could also be played as an open chord: X2022X. And you could use it in a chord progression like this one:
Bm9 Amaj7 Dmaj7
Open minor 9 chords
The keys that have been left out has no good option for being played in open position, see instead the movable shapes below. An alternative for Am9 is X0200X and for Dm9 an alternative is XX0210.
The chords may be easier memorized by compare them with other chords. For example, Em9 has some similarities with a normal C chord. Dm9 has similarities with Dm and is as a Dsus2 moved some frets. Am9 is like an Am without one part in the shape missing and also as an Asus2 moved some frets up the board.