There is truly only one way to get better at drawing, and that is to practice. Seriously, it's all about practice. People who do amazing artwork have dedicated much of their lives to perfecting their art or hobby.
As for how to practice to get better, that's the question. I've found that trying new techniques and new subjects helps expand on my skill set more than redrawing the same things over and over again. I usually make the same mistakes if I just redraw a picture, and it helps to gain fresh perspective. Sometimes I find that if I come back to an image after some time and work on it, I can do a much better job than trying to wrack my brain and force it to work the first time.
Reading tutorials can help. What I find helps more though is just using reference artwork. It makes a tremendous difference for me sometimes if I just can't get something to look right. Go look up an image, and it's so much easier.
And lastly, if you're doing this on a computer (which you are), the software can make a big difference. Getting Photoshop or Corel Painter won't magically make you a great artist, but simplistic software like MS Paint is going to hold you back. If you're not really faimiliar with high end image editing software, I can't really recommend the GIMP. Even though it's free, it will probably drive you crazy from the interface.
Perhaps you should check out Paint.NET. It has support for a lot of features that will make your life easier once you get the hang of them, such as layers and filters. There's a pretty good bit of info out there for it too. You'll want to learn to use things like this if you want to really want to improve yourself. Layers in particular are just amazing once you learn to use them, you'll wonder how you ever lived without them.