There are two methods of learning how to (or improve) drawing. Both of them have been offered in the previous posts, too! One is to start from scratch, and use a tutorial or a teacher. It's generally a slower process, but it'll build a very strong skill base that will help you in all cases. The other method, and the one that I used to learn how to draw, is to copy stuff from others. You can improve more quickly this way, but sometimes it goes awry and you can fall into using bad shortcuts and such when you draw. It also takes a keen sense of self-direction and motivation which is sometimes difficult to find within yourself. I can give you a lot of tips for the second method (as I've traveled back and forth across this path a lot, and still do), so ask and I'll fire away!
Combining these methods is advantageous in all respects, but it takes much more dedication. One thing's for certain, though (and quite cliche, as well), the more you practice, the better you'll get. Reading a guide or copying another piece once won't get you anywhere, unless you APPLY it and continue applying it until your paws die! Practice constantly, draw everywhere, and NEVER throw away a drawing, even if it's the most grotesque, disgusting creation you have ever seen!
How about posting some of your art so we can help in directing you? We won't laugh (I promise)!
