Here's a site forwardslash gave me a while ago: http://artists.pixelovely.com/practice-tools/

I took a 2D Design class last semester that was all drawing and the Elements and Principles of Design

I failed at keeping the tag up to date but here's the two posts I did do: 1 2

The next project was really cool. We first had to sketch "leave the middle open" so your eye goes around the outside of the frame.

Then we did this "unpredictable division" that was all stencils and tracing of objects and combining and overlapping them.

Then we combined both and added texture, pattern and value to create some really amazing things.

full album

If you want, I can grab the PDF assignments for the line drawings etc so you can see how we were taught. The PDFS really contain just about everything substantial from the class. The actual class was all brainstorming and coming up with ideas and working together and getting feedback and improving.

My advice is to just do it. Just get motivated, find some assignments or an end goal and do it. Practice, practice practice. Trace a lot, then try to draw without tracing. See how things come together and work together or against each other to create interesting things. Never think that tracing is a bad thing. It's learning.