From Sketch, to line art, to finished product, without the use of a tablet. (For Photoshop)
By Koiyuki
Alright, you may have read in tutorials before that the only way to truly get a good outline is to trace over the sketch by hand, with your mouse. Well, unless you’re a professionally trained art student, have hands as steady as rock, and much, much patience, you’re NOT going to want to do that in Photoshop, unless you want to get Arthritis at an extremely young age. Remember, they give you all those neat tools for a reason, use then, and use them well (although, if you happen to be reading after that line, I would assume you do NOT know how, but don’t worry, you’ll learn soon enough).
For the Beginning
For starting the piece, get a tiny piece of paper, and start hashing out a small rough sketch of what you want, and no, it does NOT have to be perfect. It can stick figures, for all we know, as long as it gets the idea of what you want for the overall piece. And always remember, if you don’t like it, you can always toss it, and start again.
Now, since I assume everyone knows how to draw, and that everyone has their own different style of drawing, I will not tell you HOW to draw your piece. If you’re really an artist, you can go by your own feel, and what you want from your art, whether it be realistic, or stylistic; Natural, or Fantastical; Wholesome, or Hentai, you choose what you want to see come to life, I’m merely here to show to how to breathe life, and color into it.
Also, for people working with sketches in Photoshop, you'll need to know these like the back of your hand.
Working the Pen Tool
After you’ve opened your file, immediately make a new layer with the New Layer button (click on the picture next to the trash can, in the lower right corner. It resembles a Sticky note being pulled up by the corner xD) Then break out your pen tool. (click on the picture that resembles a fountain pen)Select Paths (it’s the picture of the fountain pen, encased in a box xD) and click on a point anywhere on your drawing, but don’t let go just yet. Drag it out a bit, and then release. You’ll notice two levers erect from the point, but they’ll come into play later. Next, click on another point in the drawing, and repeat the process. 
Notice how it forms a path (and thus the name xD) And if you hold down Control and click and drag on one of the points, notice how you man manipulate the height and extension of the arc from each point (with their respective levers, of course, and they can both be dragged to fit into some of the more complex curves your drawing may have)
After you’ve gotten the right curve, right click and select Stroke Path, and voila, you have made a line. Now right click on one of the points, and pick ‘Delete anchor point’, then repeat the process on the rest of the sketch. After some time, and a lot of dedication. (Hey, it may be shorter, but it still needs focus, and patience), you’ll have your line art.
