If you have just recently taken up drawing or painting as a hobby, you might become frustrated because your works don't look anything like you'd like them to look.
Well, naturally lots of practicing your artwork is important. You won't be able to create a masterpiece overnight. However, it's not just important how much you practice, but in what way you do it.
Here's my advice: Don't spend endless hours trying to improve a single piece of art. If you are just starting out, this will only make you frustrated because you won't be able to get all the details right. Instead, what you should do at this stage is to improve your ability to draw the basic shapes most drawings are composed of. Over and over again.
So how do you do that? Well, there are many ways to practice this, but here is my suggestion: Download random images from the internet. Google Image Search is useful if you have something specific in mind, but this page is pretty good if you want to draw people and faces.
Now attempt to draw these images as accurately as possible - within only 10 minutes!
Once those 10 minutes are over, put your drawing away and move on to the next image to draw. Even if it looks unfinished and you'd like to add more details. Like I said, at this stage you shouldn't worry about the fine details but about the basic shapes of what you are drawing. This kind of practice will teach you how to do just that, and the progress you will make in short order should be obvious.
Note: I've used computer images for my own practice because I also draw digitally on the computer, but of course this isn't required - if you like to practice with an old-fashioned pencil, you can easily use pictures from books, magazines, photo albums or even real life objects as inspiration. But the basic approach stays the same - work only 10 minutes or less on a single piece, and then move on to the next.