Personally, I let a random number generator dictate my 3 exercises. I do this because I feel that it's important to do them all, rather than stick to the 3 usual suspects (superimposed lines, ellipses in planes, organic perspective.) If you decide to do this, and notice that the rng gods like certain numbers more than others, feel free to have a system where if you roll the same thing 2 days in a row, you get to skip it, and roll again. As for the rotated boxes exercise and the texture exercises, feel free to do 1 quadrant of the former, and skip the latter. I don't do this myself, but it might be a good idea to have a page for each exercise, and work on it for 5 minutes every time you roll it, and then leave it at that (incomplete as it is), to come back to it next time. Anyway, regardless of how you decide to go about it, make sure it doesn't exceed the 15 minute mark, lest it defeat the purpose.