What is your best advice for someone who wants to learn art?
It's nice to have a God-given talent in art, but actually anyone can learn it (as with most things if one is determined and disciplined enough). My first college major was Commercial Art, and I went through a year of classes, but I didn't stick with it; saw the need to get a degree closer to my military experience (aviation) for my job.
1. I recommend at first learning how to 'see' by drawing everyday objects. Start with simple objects around the house, like a mustard jar, apple, orange, even a pencil laying on a table, etc.
2. The way I taught my boys how to draw was actually to draw an apple and then tell them to color it with their crayons. The natural tendency for most is to color the apple all the same color of basic red (called 'local' color), which they did. Then I got them to look closer at the apple, and notice that much of the bottom portion was in shadow and thus a darken tone of red, and even there was a slight yellow blotch on the top in one corner.
I told them don't draw or paint what your 'mind' tries to tell you how an apple should look. Everyone knows an apple is red, so they ten to make the whole rendering red all over. Draw or paint what your eye 'actually sees', like a camera. This is kind of difficult to do at first, but it is the beginning of developing what is called the 'artist eye'. Some naturally have it, others must learn it.
Move your hand back from the lead end of the drawing tool, get loose when sketching. Don't be concerned if you don't connect all the lines in your drawing, it's actually better to leave some disconnected (the viewer's mind will automatically connect them). I've always used short fast motions when sketching. So that is a long ways away from trying to 'outline' what I draw, because anyone can buy a coloring book with clear, thick outlines of objects that is lifeless. Want your drawings to have life, then don't think in 'outlines'.
3. Learn perspective. In drawing class, they teach you about perspective and the vanishing point, etc. It may sound boring, but it is actually pretty essential if you ever want to develop into major graphic design work and landscapes. I had 2 years of mechanical drawing (drafting) in high school, and another year of engineering graphics in college. That pretty much training my sense of perspective to where rarely do I have to draw a vanishing point into the sketch prep. It also helps to 'see' angles of various objects that are near each other, like for a still life.
4. Color Theory is another area that the artist must get a grasp on. Lot of it has to do with physics too like perspective does.
5. Learn to paint in oils. Most professional art classes will have you start using oils, because they are very forgiving. They are long drying, so you can correct mistakes easily. And though software art programs are great tools, they still have yet to capture much of the feeling of painting in real oils. Watercolors is a different ball of wax, because it is more technique driven I think. With oils, you get to see the strength of color you're laying down right then (usually). But in watercolors, a color will dry lighter in tone most of the time.
I highly recommend an art instructor, if serious about making it a career. If not, then most communities have seminars and art workshops where you can pick up a lot.