If you are totally new to watercolor, try reading through my short guide on How to Get Started in Watercolor.  Otherwise, I strongly recommend starting with my 5 class Introduction to Watercolor Portraiture course, or at the very least working through Fundamental Techniques. If you have already covered this material with me, you may enjoy the Advanced Tutorials!  Artist who are already very comfortable making, controlling, and layering multi-tonal gradients may find the Advanced material accessible, but please keep in mind that these tutorials assume facility with these techniques. 
Multi-Session Courses
Single Tutorials