This is one of my favorite tutorial that you should peek. I don't have to say so many words but CLICK THE LINK! :D
For your information, this is a tutorial of traditional inking, which means you really use pencil and pens and papers. Inking for digital work will be -- somehow -- different. But once you master or understand how to inking traditionally, you will have no problem to do digital inking.
One thing, you have to download the tutorial to see the written n pictorial description. Just click the button "Download Image" at the page and you will get the real tutorial page.
No further talk, this is the link:
Traditional Inking Tutorial page: here