These studies were mostly created during university (Zurich Art School), where we focused on realistic illustrations and drawings, mostly.
While the very basics like ink stippling, crosshatching and ink washing, as well as the very classic pencil perspective drawings, didn't create any sort of final 'product' to hang on walls, they were good practice for later works.
The watercolor / aquarelle course was sadly short for such a tricky medium, but we started with simple pencil sketches (very light strokes!) that we then colored in from observation. The colors were limited to a cold and a warm tone of each hue, and we worked from cold to warm (as it is more difficult to make a color colder once on has erred on the side of to warm) and added final highlights in white guache.