1) There are no rules. There are ways of gaining skills, but no rules.
2) What do you want your drawing/painting to look like? Do you have (a) favorite artist(s) whose works you particularly admire? Find someone to emulate because it gives you a first standard toward which you can aim. It gives your efforts specificity. It doesn’t have to be etched in stone. But you need specific goals so that you can make progress that is measurable. My first hero that I remember was the French 19th century painter Edgar Degas, but even before that I had heros even if I didn’t always know who they were — various artists whose works illustrated books, magazines, etc.
3) What are you looking at in making your painting/drawing? If you are not looking at something, you need to start. Just drawing from your head will greatly limit your ideas. Have something that you are looking at and attempting to copy — either another artist’s work that you copy to learn, a photograph that you copy to learn, or an actual three dimensional subject. Or all three.
4) Remember that something is going on in every part of the picture. Even a continuous tone is “something that is going on.” Make sure that some of your attention wanders toward the “insignificant” parts of the image so that everything can be part of the whole. Even if you are leaving part of the page blank, that blank can read as a decision rather than an afterthought.
5) Pick something that you really like so that it can fully engage your attention. If you draw a vase, choose one that you find fascinating to look at — because your attention becomes the picture. If you are looking at a real blue vase, start noticing its whole surface with the attention of a lively tourist ant that crawls around on all its parts. As your attention wanders ant-like, notice the specific color of blue in exactly that spot and how it is warmer or cooler, lighter or darker, richer or duller, than other adjacent parts of the vase. How dark is the darkest dark? How light is the lightest light? What is in between? Does the blue have subtle qualities of other colors hidden in it? A slight bit of yellow? Or of rose? Or deep purple? Of warm green? Other colors are present even in an object that seems to be “just one color.” Whether you choose to depict those other colors or not, learn how to notice that they are there.
6) Think not just about the thing but about the spaces between things. Get two vases — or a vase and a lemon — or two lemons, an apple, a vase and a bowl — and put them together into a group. Start noticing the relationships between the objects as much as the objects themselves. If it seems hard, that’s good. It forces you to see shapes and forget things and names of things. Wrestle with it. You have lots of paper. You can make drawings first and paint later. Draw and redraw the same thing, always looking for what you find most appealing in your subject.
7) Sometimes make yourself draw quickly. Sometimes make yourself slow down. Draw the same subject from different points of view, or at different times of day. Draw something you’ve never drawn before. Draw something you’ve drawn many times. Shake things up. Sometimes do the opposite of whatever you usually do. And inside it all, find joy. Joy may prove at last to be the best teacher.