This tutorial is 5 steps and it has a difficulty level of Easy. This tutorial should be great for new users to PhotoShop to show you a few basic things with the program. This Tutorial will show you from start to finish how to add those trendy scan lines to all of your images to give them an extra bit of detail.

     1. Start off with your original Image opened up in PhotoShop, I chose this screen shot I took from the intro to Savage, The Battle for Newerth created by S2Games.
Step 1

     2. Now, create a new image 2 pixels in height, and 1 pixel in width. Make sure it has a transparent background.

     3. Select your paintbrush tool, and make the size of the brush 1 pixel. Turn your foreground color black, the hex code is 000000. Now you need to paint a black square at the very bottom of your image, zoom in as far as you can before doing this so you know exactly where you are painting. Your 2x1 image should look like this, except without the white.
Step 4

     4. Go to edit then go down to define pattern and click it. Now name it Scan Line or whatever you want to name it then press OK.

     5. Go back to your original image then go to edit now go down to fill and click it. In the Contents box for Use: select Pattern from the drop down menu. and for Custom Patter: click the down arrow and find your Scan Line pattern we just made and defined. For the Blending box, select Normal for the Mode, and 100 for the Opacity. Now you need to press OK and your result should be like the below image.
Step 5

     Optional: Go to edit, then down to Fade Fill and press it. Now play around with the Opacity to get it how you like it to make the lines less visible. 100 is the most visible, and 0 is the least visible.