Sharpening

To counteract the blurries in both the input and output stages, you need to sharpen your images. Photoshop offers several sharpening tools, but Unsharp Mask and Smart Sharpen are the only ones that really work as production tools. The Sharpening tool and the other sharpening filters may be useful for creative effects (and even then, we prefer other approaches), but they'll wreck your images very quickly if you use them to compensate for softness introduced during either acquisition or output.

Smart Sharpen is the new kid on the block, and it's pretty interesting, but if you want to understand sharpening, the place to start is the Unsharp Mask filter. It's easier to understand, and faster to execute, than Smart Sharpen.