Enroll in an art school. Google "art school" and the city you live in to find the right school for you. For instance, Watkins College of Art, Design and Film offers degree programs in interior design and painting in Nashville, Tennessee.
Take night and weekend classes in painting and decorating at a local community college. Also look into painting and decorating classes at local arts centers. Also investigate if local artists teach classes in their studios.
Apprentice under a well-known painter or decorator. Interact with a qualified painter one-on-one to learn about the business and craft of painting and decorating. Do an internship for credit, if you are a college student.
Learn about contemporary painting and decorating techniques. Enroll in an art history course to learn about recent trends in art. Go to a local bookstore and read a book about contemporary paintings and decorating trends.
Copy paintings of master painters for practice. Closely examine the brushstrokes and colors. In addition, teach yourself to draw by copying masters such as the painter Tiziano Vecelli. Use these drawings to learn proportions for painting.