Well, you should memorize the fretboard notes and the notes of the scale...
Harmonic Minor is this formula based on the major scale: 1 2 b3 4 5 b6 7

So apply that to any major scale, say C major, C D E F G A B...

Then C harmonic minor would be C D Eb F G Ab B

Hope that helps abit
the easiest way for me to remember the harmonic minor scale is that its the exact same as the natural minor but with a raised 7th.