If you want to maximise your learning from any source—a book, a video, a live people, or online lessons—keep these guidelines in mind.
First, finish and understand each subsection before moving on. Make sure you fully grasp each new skill or concept in your study before moving on. Attempting to skip ahead without fully understanding a lesson will only lead to frustration and wasted time.
Second, put in the effort you would if you were actually in school. Get your nightly dose of homework done. Only spend those 15 minutes wisely if that’s all you have. The application of the last lesson or drills like scales and chords should be done if you don’t have time to study or watch and apply. Most of the time, you’ll have to unlearn what you’ve learned from reading or watching something if you don’t get a chance to put it into practise right away. Write things down. Especially whether you’re dealing with a human or watching a video. Don’t be shy about marking up your worksheets or music sheets, either.
Put your new knowledge to use: Participate in the performance for the benefit of others. The congregation you attend, your loved ones, and the unused piano at your local department store (ask first). Recitals are the best way to cement what students have learned in music class. It will also highlight your areas of improvement.
Anyone, young or old, can benefit from these guidelines. Taking up an instrument is a lovely pastime.