Complete a basic drawing. It would be best if the drawing were completed in pen or pencil without color, at least until your digitizing skills improve. For now, create a simple black and white drawing.
Place your drawing on the scanner bed. Be sure to orient the drawing to the upper-left corner. Close the lid of the scanner.
Open Photoshop. Select File>Import>Scanner. (Note, if you are using a Twain-brand scanner, it will say "Twain" not "Scanner.") This will let Photoshop know you intend to scan directly into the program, opening a pop-up window. Select scan and the machine will begin.
Observe the preview of your drawing. At this point, before saved as an image, you can adjust the size of the image and the canvas. This means that if you have a small drawing on a regular sheet of paper, you can crop out the rest of the black page so you only have the drawing showing.
Enhance your drawing by tracing over it in a new layer with the pen tool. Often if your original was in pencil, the scan will be faded or appear smudged because it picked up all of the eraser marks. Create a new layer and trace over your image to clean it up. At this point, you can also add effects and colors, but be sure to delete or turn off the original scanned layer so none of those old mistakes show.