Draw from life. Measure the proportions, this is twice the lenght of the height etc...
Get a perspective book and read it. Then try to draw real life objects in propper perspective.
Wether you want to draw toony or realistic, the principles are mostly the same.
Learn to make confident lines. Avoid drawing with a fuzzy line, it's an inefficient way to draw I think (tough you can make the line fuzzy afterwards).
Draw sculpturally, meaning you should approach everything as a 3D form and not just as an outline of a object.
Learn when to draw very lightly and when to make a good hard line.
Do lots of studies of your hands, this will pay of when doing organic shapes.
Draw yourself infront of a mirror, look at the shapes and look at the way your body deforms when it moves.
Simplify! Try to find basic shapes in everything like box or rectangle, triangle or cillinder, etc...
Work large to small, general to specific.
Download Andrew Loomis' book "Succesfull Drawing" and read it and do the exercises.
http://acid.noobgrinder.com/Loomis/If you want to study anatomy, try doing lots of studies from these. They don't show every muscle, but show the basic form well.
http://www.angelfire.com/art3/kchendemos/ (warning: lots of images)
Don't forget to do stuff besides anatomy tough!
There are crutches everyone needs to go trough, they can be very frustrating but it pays of once you get the hang of them.
But most of all, just try to have fun! And draw every day!