Not what – how!
I’m going to just say it straight off the top: what you practice is not as important as how you practice it. Here are some basics. I’m going to elaborate on all of them, but not now.
Use a metronome or other timekeeper
I have more than one, but I haven’t always used them. I now believe in using it every time I practise, but not necessarily for the entire practice. I mainly use Pro Metronome by EUMLab.
Drum machines are also good, and I spend time with Drum Genius.
Listen carefully to the drum loop, measure its length, surf on the meter, breath and move your body following the time feel. When you feel comfortable, play or sing, trying to groove with the loop as much as you can and remember: DON’T MISS THE ONE!
Mauro Battisti (creator, Drum Genius)
Read music
This helps me focus and improves my memory. My ADD-aware approach is to look at the entire page while breathing through my nose to lower my heart rate. I try to take it in all at once, noting time and key signature, dynamics and form. My goal for reading is to hear it in pitch even without my instrument.
I’m not a fan of tablature, especially when it has no rhythm. It makes it even harder for me to follow the staves.
Scales, double stops, triad inversions
Segovia’s fingerings are awesome — but incomplete. I now try to know his fingerings, but mix and match the position changes. The Berklee two-octave scales are an important aid in this. Segovia gives you 3 or 4 fingerings that work for all major and melodic minor scales in all 24 keys. The classic melodic minor scale’s descending form is the natural minor.
The 7th mode of the jazz melodic minor, also known as “the altered scale,” is an important one Segovia skipped. The first 4 notes are a diminished scale, and the next 4 are a whole tone scale.
I’ve done fingerings based on Segovia’s and Berklee’s (William G. Leavitt’s) for all the church modes, which I’ll post here eventually.
Thirds, sixths and tenths are the obvious double-stops to begin with, and chromatic octaves. This chromatic octave exercise is often the first thing I do when I pick up the nylon string guitar.
Relax
Breathe. Meditate. Seriously — practice can be a form of meditation. For me it has to remain mindful. I support The Medito Foundation and I use their app for guided meditation.