Actually, you're doing just fine, man. Shading and lighting can be tricky, heck up until last year, I had no clue how to even do it at all! It's really easy, though. First thing to know is the direction of your light source. Once you have placed your light source, the next step is color and intensity. Think of the atmosphere you want to go for and do a couple of thumbnails with the scenario. The final step to making any lighting setup look just right is knowing how it flows or covers the surface of the subject/character. Always remember your character is a 3 dimensional object and depending on where the light source is, the shadows and highlights will fall in different ways, so just break your character down into simple shapes.

It also depends on what style you're looking for or what medium you want to replicate or simulate. You have a very desaturated, bright and watercolor looking style of lighting. Try different types and directions and just experiment with lighting. Sooner or later, you'll become a pro at it. Also, here's this, which I found very helpful as well- http://farcry692003.tumblr.com/post.....ading-tutorial I hope I was able to help! Keep up the good work, dude!

Ohhh, that really useful ! :D
Thanks a lot man !

No problem, dude! Glad to help!