In the past, I have not been very good at planning my practice time when I learn a piece on short notice. If I have two months, for example, I tend to do most of the practicing in the last two or three weeks... and this has a negative effect on the quality of my performances (Walton and Mendelssohn come to mind). Now that I have three weeks to learn the Brahms G minor piano quartet, for once, I am realizing at the outset that I have to make some kind of plan, if I am going to produce a credible runthrough. Even though this is a pickup group and we are only playing for each other, I would still like to be prepared and reliable.
Given that weekends are unpredictable in terms of how much time I will have to practice, and given that Carol works weekdays, likes attention, and is a bit mercurial when it comes to how she plans her weekends, I have sixteen weekdays, counting today, from now until the 27th, when I am meeting with the string players. The quartet is a massive piece - four movements, each about ten minutes long. Instead of starting from the first movement and working forward, which is a bit open-ended and likely to result in unhealthy cramming for the final movement at the last minute (see: Hindemith), I intend rather to give the most practice time to the most difficult passages, which means that I will learn the movements in the following order: fourth, second, first, third. So today, Friday, Monday, and Tuesday, I will work on the Presto finale. Wednesday through the following Monday, I will add the Allegro intermezzo - it is fast and light, which is the most challenging sort of playing for me. The rest of that week, I can work on the Allegro opening movement, and then I can spend the week of Monday the 23rd working on the Andante. I did not count Friday the 27th among the sixteen days - it's rare that practicing anything the new on the day-of can be of any benefit. That will be a day purely of review.
Granted, the movements are not all equal in difficulty, even though I divided the sixteen days up into four equal groups of four days. But in reality the more difficult movements will get more attention, as I will be only playing the Presto at first, then two movements together, then three movements, then the whole piece.
That is a plan, at least. My plans frequently don't quite come to fruition as I naively expect them to. But having made a plan in this case is progress for me.