In my course with Ross, he recommended that I begin with understanding the note layout on a 12 hole Chromatic Harmonica, specifically the location on the harp for the notes of a C major scale. As the diagram shows below, the notes and relative hole assignment is the same across all 3 octaves. It is important to see that the C pitch appears twice tween each octave. This one of the first things that confuses a diatonic player, but your brain quickly learns to ignore this. When playing a "blow" C, the one you select will be determined by where the following note lies. As we will see, there is actually more options for finding a C.
This is where some memorization begins. Memorize CEGC as the repeated note pitches assigned to the blow holes on your harp. Memorize DFAB as the draw notes on your harp. While the initial curriculum from Ross focuses on playing by ear, I wanted to make sure that if someone says play an "A" that I could do that in any of the 3 octaves. Further more, if I saw an A on music notation (sheet music) I could like wise play that note. Ross suggested making a set up flash cards with the C scale notes on individually on them: CDEFGABC Then practice playing those notes each time one was revealed with a flash card. If you have memorized CEGC and DFAB, then that will make it easy. If flashcard with an A shows up, simply think DFAB and realize 3 draw will give me an A.
I made the following video to that includes a reveal of a note along with a display of that note on music notation. As quickly as possible, I play that note in one of the 3 octaves. When the card flips it plays the correct pitch to give me feedback on whether I picked the right note. It did note take me long to get the right answer in the 1st octave. I am still working getting it right in the 2nd and 3rd octave. The trick is to know where each C is and think of that as the beginning of the scale.