Draw. Draw what you see. Draw what you don't see. Draw any time you think of it, whenever you put pen to paper to do something else. Draw in a sketchbook. Draw on the corners and margins of your shopping list. (If you get a good one, paste it in your sketchbook to look back on later.) Draw elementary geometric shapes and solids. Draw bent sheets and banners. Draw perspective. Draw a thousand roads disappearing into the horizon. Draw a thousand castles with crenelations and gates and towers and a flapping banner on top. Draw an apple, an orange. Draw texture. Look at the way the light hits something and reflects. Study shadow. Study how everything on your desk is made up of the elementary shapes you learned. That's a cylinder. There's a plane, and a box with rounded edges, and that's a box that got itself confused and got sent to the cone factory, with little fiddly bits. Discover the drape of cloth. Discover the drape of this cloth vs. that cloth: how lightly cotton lies, how stiff suits wrinkle despite themselves, the drape and swish of heavy knit. Draw motion. Watch the blur of this into that, figure out how to draw the transition, which things are necessary to convey the whole and which you can leave out. Draw cartoons. Draw the realistic, every little grain of sand. Simplify. Exaggerate. Study. Work from a photo. Work from life. Learn the face, the body, all the different eyes and noses and ears and chins you can find. Learn all the colors of every part of your own skin. Learn someone else's. Find work you admire and reverse-engineer it. Find an artist you admire, find five, and watch them work if you can. Learn your tools. Stretch their limits. Make printer's ink work like watercolor. Stack watercolor like tempera. Try acrylic, oil, oil pastel, crayon, highlighter, whiteboard marker, pencil, your own blood if you have nothing else. Distinguish the constructive from the non-constructive, and discard the latter. Is "that sucks" really "that's not to my taste" or "your execution was poor", or both? Don't stop. If you stop, start again. Start with something elementary and simple and stupid if you have to. Go back to basics. Draw what you see. Draw something else. Look at the others in your field. If "[you] could do better", do it. Start over. Throw it all out if you have to (and give some to somebody who won't, and scan it first in case you change your mind). Keep going. Plop some up on the internet. Figure out what tools you're missing and save up for them. Blow too much of your grocery money on art supplies and decide you like the taste of ramen this week. Try not to do that again too often. Accept a commission or two. Figure out what they can't pay you to do. Struggle with a dozen different art programs. Learn how to scan. Learn how to modify something you sketched up into something with colors that nature didn't make it easy to get to.