With so many things to practice, how do we manage it all? How do we successfully cover multiple areas of guitar and music in one sitting? Even if that sitting lasts only 30, 20 or even 10 minutes?
I would like to advocate this technique of practicing in which I have subscribed to, although i'm not totally consistent with yet, as I am still striving to make it a habit. In times where I have used it however, the benefits in helping manage practice items and staying focused have been apparent.
The idea behind this, is to set a timer for every specific exercise or practice item in your list of things to do. The length of time for each depends on your choosing and the time you have available. If your goal is to cover multiple things in a short space of time, let's say 6 items in 30 minutes, a good example would be to set a timer to practice every item for 5 minutes each. Of course, the amount of time allocated is still up to your preference. (Maybe you'd want to spend 15 minutes on one item and 3 minutes each on the other 5.)
The first benefit of timed practiced, is that it ensures that you cover everything you need to in the time that you have available, within reason of course, (trying to fit maybe 100 items in 30 minutes may be a bit too much to manage).
Secondly, by setting a timer to a task, you instantly set your mind in focus mode, as your brain is less likely to take on distraction knowing that you are to do nothing else but to practice that item for the next couple minutes.
Thirdly, knowing that you are currently focusing on a single task for a known, limited amount of time, increases the likelihood of your concentration on that task, helping to making the best use of those couple of minutes while increasing the results.
Another benefit, is that it gets you into the habit of making the best use of small amounts of time. Many times musicians, including myself won't bother to practice if they do not have the amount of time they think is ideal for their session (Sometimes if I can't get a full hour or at least half, I won't bother to practice at all!). As an example, that 5 - 10 minutes you have before leaving for school or work on a morning is actually an opportune time to zone in on this idea.
It is surprising how much practice can be done a few minutes. To really observe this yourself, try breaking up your practice items into smaller chunks of time, maybe between 5 to 15 minutes each. If you want to spend an hour behind practicing a particular scale, try setting the timer four times, for lets say, 15 minutes each. Practicing this way, with four countdowns would also help to reset your focus as the timer is reset, as our brains tend to go on autopilot very easily when working on one thing for a longer periods of time. Also, by practicing in small chunks, you can also spend a total of one hour practicing these scales but in between other practice items, instead of doing it all in one go.
I can say that this method of practice has really been beneficial for working on multiple items and for getting the most out of my time. And I strongly suggest trying it out yourself to see how it could benefit you.