Speaking of different papers - or supports, here is an interesting and informative exercise that I first saw in the book "Painting in Watercolour" by Jenny Rodwell.  

Line up several kinds of papers as shown above, and paint a scene across all of them.  As you do so, you will learn about how each takes the application of pigment and the resulting effect.  Try different approaches such as wet-on-wet, wet-on-dry, washes, caligraphic strokes, etc.