Teaching guitar is hard when the student hasn't been bitten by the guitar-bug yet. The best way of gauging whether a person has been smitten with guitar is if asking them to spend five minutes a day on guitar inspires thoughtfulness, or groans. If a person gets to the point where the vista of playing guitar opens up to them, where the possibilities are limitless, that five minutes of practice every day is no longer a chore. It's fun. After this point, the person plays guitar because they enjoy it, and not because some schmo like me told them to practice.
Recommending for any student to practice an hour a day might be overkill. Students who hear that are usually filled with dread for the next lesson. "Practice if you feel like it," admittedly my old credo, is just as bad. It encourages the student to do nothing. Five minutes is arguably just the right amount of time. Most of the time, as long as a guitar is on a guitar-stand, in plain view, begging to be played, it is easy to pick it up and play it. Give it some time, and you won't think it is a chore.I must say that out of all the people I have taught, there were only a couple of persons who stayed in lessons even though they didn't put in five minutes a day on the guitar, even though they were not smitten enough to really play it. This is so interesting. Why stay in lessons if you don't even think about playing it outside of the lesson? Was I that funny (doubt it)? So now I'm resolving to do something new: I am going to do a lot more teasing. It's all in good fun, and in the name of enjoying music.