'Practice what you'll have to draw soon' is my MO, too. Also 'I have to draw so, SO many trees!/at least it's better than buildings' is my chapter one in a nutshell.
Alas, now I'm onto chapter two, and there are mostly buildings. Especially libraries. Let's just say my perspective-drawing skills are getting a workout, especially 3-point perspective. (My RSIs and I are going to cry in a corner for a while, no worries...)