I have been doing art-stuff for about twelve years now - for the most part painting and 3d modeling and a little bit of drawing. It was only about a year ago that i have started to seriously learn and practice to draw - before that i have always used posed 3d models as a starting point for a figure drawing.
As for tips - learn how to construct the things you want to draw out of a few basic shapes (circles and lines). When you understand the anatomy of something it is easier to draw it in new poses and perspectives.
Learning about facial expressions and body language is also very important.
There is also the good old tip "draw a lot". - I have spent a lot of time during the past year to make lots of practice sketches - reconstructing the sketches of other artists (especially things like the developer sketches of the "fighting is magic" character pose sheets that are available on their website).
During season 2 there were the marathons before every new episode - i have spent some time watching them while speed-drawing expressions and poses of the characters as fast as possible. At first it took about five minuted to draw something the may or may not resemble the intended character - but as the season went on i got much faster and better, managing to draw something presentable in under a minute.
You can find some interesting tutorials in the "useful" folder of my favorites collection here on deviantart.