One of my favourite things to do is to swatch colours. It's a great way to become familiar the properties of my paints and I think it's pretty, too. Plus, and this is a fantastic bonus, there are no mistakes in swatching. :) I like to use my waterbrush, large and small brushes with water, trial colours on different types of paper (ie. mixed media, hot and cold pressed watercolour papers), and try different colour mixes. I also try out blooms and bleeds and salts and tissue to create different visual textures. Then, once I'm done, I tend to put these colourful little papers away for a future altered book project, so that for me is a win-win. Plus it's a fantastic way to use up scraps.