I've already prepared the penciled drawing of Lee for digital inking, and have zoomed in on her face about 50% of the actual size.

 

Make sure that your foreground color is set to Black.

What I'll show first is using the Pen tool to trace outlines of your drawing and fill it up with black color.

Select your Pen Tool (P) .

Be sure you are tracing on the Ink layer. If you have no idea what i'm talking about, you may need to read my tutorial on 'preparing your pencils for digital inking'.

I always start my inking with tracing the eye. This is a reason why I try and make my pencil lines as clear as possible, so that when I trace, I pretty much know how i want the details to look like, an example is the shape of the eyes.

Using the Pen Tool will be a lot easier and faster if you can master using your tablet or mouse on one hand while using the shortcut keys associated with the tool with the other.

On the right you'll see that I've completed the trace of the general shape of her eye and eyebrow. You can go back between paths and do some tweaking until you're satisfied with the shape. Make sure your paths are closed.

 

What you want to do now is right-click (Windows) / ctrl-click (OS X) somewhere in the canvas and select Fill Path. Fill it up with black, your foreground color.

After filling your closed path with color, you can delete the path you've made. On the left is the result of what I did so far.

At this stage, you can go ahead and trace the rest of the face's detail, like for instance her eyelashes and irises.

I use this tracing technique on basically the eyes, as I am particular with how my drawings' eyes are shaped, and for me the best way to achieve what I want is trace and fill the path.