I usually do my line art in Painter 9 using my Wacom Intuos. I start bysketching straightaway directly in Painter. You might want to draw your sketch on paper and scan it in. 

Painter tool used: Brush - Pens - Scratchboard Tools 

Happy with the sketch, now I go on to inking with the same Brush settings. Work with flowing lines and make good use of your tablet pen's pressure sensitivity to create lines with different weights (thickness). It requires practice, so don't give up if your lines doesn't turn out well the first time! 

Painter tool used: Brush - Pens - Scratchboard Tools &  Brush - Eraser - Flat Eraser  

Tip: Press [ALT]+[Space] keys on your keyboard to turn the canvas, it will help to angle your brush stroke.  

When done with the inking and happy with it, delete the sketch layer and you will have a clean line drawing! Since I will be coloring the picture in Adobe Photoshop, I save the file in PSD format, with the layers intact. (do not drop layers onto the canvas)   

Open the PSD file in Adobe Photoshop. First I need to resize the picture to the required size. 

In this step I want to set up a rough guide to the atmosphere. Using the gradient tool, I draw out the background - Sky and Water.   

Photoshop tool used: Gradient Tool