Recently, two of my friends, Sisavanh Phouthavong and Lizzy Rockwell, posted a series of watercolor sketches on their instagram accounts. I was so inspired that I went to Central Park with my friend, Mary Kay, and we did watercolor sketches.
There are no hard and fast rules to watercolor sketching. We found it helpful to set a timer for our first sketches, just so we would go for it and work to complete the paintings quickly. The more comfortable we got, the less we needed to be pressed with time.
You don't need fancy materials, just any watercolor paints you feel comfortable with and a small pad of watercolor paper. Let the adventure begin, set the timer or don't, just have fun and be free.
Here is a helpful website, I came across after writing about watercolor sketching: Andy Walker's Sketching Tips - Watercolor Sketching.