The only advice for drawing is what my brother used to tell me when I was a kid:
Start simple... Just use circles and squares/rectangles, then add more edges... Then, once it's proportioned properly, fill in the details, and erase the unnecessary parts. Don't push hard on your pencil, and don't try to make perfect lines. Go very lightly, and somewhat fast. Don't think too hard. Each stage will help your transition to the next, and things will fall into place. (It helped for me).
Look online for beginner and intermediate drawing techniques. There are alot of good resources, even video tutorials. Some of them are pretty helpful!
And don't give up... Just practice alot. If you get too frustrated, STOP and come back to it a day later. Don't push yourself, or you may make more mistakes and get twice as frustrated. Remember: Some days you just can't draw at all, while others, you're great. I think that goes for everyone... Just ask the people here. I'm sure they have had those days many times.
Hope that helps a bit.