Thanks to a lot of generous people there is a an amazing availability of art tutorials online. These are a great way of getting your feet wet if you are new to art or a certain medium or simply looking to challenge yourself if you have some experience already. Even as an experienced watercolor artist it is interesting to see how other artists work - everyone has a slightly personal way of doing things or has found a particular thing that works in addition to the fact that there are many ways to get good results.
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While you can learn a lot from these tutorials, I do think there is no substitute for learning from others. This is where taking a class or getting together with a few fellow creative souls will help you learn from each other. But that said, I have learned most of what I know from books, experimentation and online tutorials. This way I got a ton out of the few classes I have taken, because I already came prepared with the basics.