Well here you will be taught how to create gridlines using Photoshop. This is one of the most basics effects to do so you shouldn't have any trouble. If you already took the scan line tutorial, you'll see this one is very similar
1. Click File> New and use these settings. Make sure its on pixels. Later once you need different size grid lines you can change the height to accomidate that.
2. Next with the color that you want your grid lines to be, usually black. Fill in the first row and first column using the pencil too. Then click Select > All.
3. Now go to Edit > Define Pattern. This will set this as the pattern.
4. Now click the image that you want to put the grid lines on. Click Edit > Fill. A box will pop up. Make sure it set to Pattern not Foregraund Color. Then just hit ok.
Extra
To make your grid fade use a large size eraser, 200 or 300. then erase the parts of the grid you don't want, it will appear to fade.
More Tutorials: 
