This is a really long question. There are lots and lots of different things that can improve your drawing. What always frustrated me as I was trying to learn is I didn’t know where to start. When people say “Practice” it makes me want to scream. If you don’t know what to practice it feels like going in circles! It’s like teaching someone how to drive a car by giving them a heap of parts.
anyways rant over… here’s some advice lol
1. Get a sketch book and some pens (various types to see what you like) Go somewhere, (anywhere, park, mall, subway, soccer field) Sketch from LIFE!!! This is the best exercise you can do by far. Do quick sketches of what people are doing, Don’t worry about details or outlines, heck, use a crayon. Draw lots of gestures, are they sitting, standing, leaning. What leg are they resting their weight on, what way are their shoulders tilted, are they tall and thin, are they short and fat.
you want to work quickly, while trying to incorporate as many things you know as you can. This will help with showing movement, proportions, mood, and general drawing.
Don’t worry if everything looks terrible at first, gotta start somewhere right!.
2. Practice Proportions
just spending time practicing proportions is a good way to put them in your mind and eventually your sub-conscious.
Find as much info as you can about proportions, there are 2 main systems, the head-system (a person is 8 heads high) and the 5 eye box system {(the one I prefer), the head is 5 eyes wide, from the top of the head to the pit of the neck is 2, 5 eye boxes) Find these and practice drawing from them. Memorize important land marks, the half way point of the body , how long are the arms, legs etc… There’s lots of stuff out there to look up.
3. Learn perspective, 1,2,3 point, curvilinear and atmospheric. Start with 1 and work your way up. Perspective is essential to drawing anything. It helps create depth and realism in any image. Start out by drawing cubes cylinders and various other simple forms, and then start breaking more complex objects down, a bike is just a series of cylinders. A hand is a box with cylinders for fingers.
4. Anatomy. this one’s kind of advanced but is essential. Practice drawing skeletons, this will help with your posing, and proportions. Then move onto drawing the muscles. If you know your bones and muscles you can draw a person doing absolutely anything.
I always recommend life drawing to people because it’s very challenging and you will learn so much. A wise woman once said to me there is no problem in drawing you will face, that you wont face in life drawing.
Painting adds more complexity - you’ll also want to look into tone- shadows / lights and color- which is a whole great big challenge on it’s own.
Good luck! - www.conceptart.org -> my favorite website, head to the forums, very useful!