Updated: Jan 4, 2020
WHAT? It starts with habit! Psychology suggests it takes an average of 66 days to create a new habit. If you can sweat it out, and be patient, not breaking your new routine for 66 days (everyday), research suggests you will have an entirely new habit!. An example of this might be squaring-off 30 minutes everyday, typically around the same time - and being totally committed to these 30 minutes. With no distractions of a smart phone or television, keep these minutes totally focused on guitar. Maybe even try it for 21 days and see what happens! 21 days is nearly perfect in my experience.
The Non-Negotiable Rule
CAREFUL! Weekends and holidays are generally the time when we neglect, forget, or take time away from the new habit. This CANNOT happen; you must have “stick-tuitiveness”. Try it; I DARE YOU! I call this the "non-negotiable" rule.
WHAT DO I PLAY ON A REGULAR BASIS?
II. Have a concept of what you will do.
In this half-hour I would strongly suggest scale and arpeggio practice. Scale and arpeggio practice is a fantastic way to strengthen posture and muscle memory in both hands. Below is a most standard scale formation and an arpeggio which are both movable (starting in G). Follow the exact fingerings listed underneath each example; this is vital for standard practice. Perhaps 20 minutes in pick-style guitar, and 10 minutes for right-hand fingering, PIMA. Consider finding a simple piece like Waltz in Em by Carulli, or Allegro, Opus 50, No. 13 by Giuliani. These are great exercises for right-hand (fingerpicking) PIMA. I play these exercises and similar classical works everyday, as I believe this is key to maintaining solid guitar skills. Go for it!
 Page-Bottorff, T. (2016). The Habit of Safety: Forming, Changing & Reinforcing Key Behaviors. Professional Safety, 61(2), 42.