I usually have two builds going at the same time. When one gets into the paint and decal stage with all the waiting, I start another kit to have something to work on.
How I choose the kits I build can vary greatly. Sometimes a movie, documentary, or Finescale Modeler magazine article will spark the inspiration, other times a build on this forum will motivate me to pull a similar kit from the stash. I've had kits that turned into a grind, so the following kit will usually be one that I hope will be an easier build. With this corona thing going on, I've been looking at my paint supply as a factor in build choice. I try to avoid mail orders as much as possible, so I've been leaning more towards the 1/72 and 1/144 scale.
So, how do you choose what to build?