Amy Hood of Hoodzpah drops this quick tip on how to create a retro, grainy texture effect on your images in Photoshop. Using Filters such as Diffuse, Dust & Scratches and Noise you can quickly dial in the right amount of grain to your liking. There is even a Photoshop Action you can grab for free that automates the steps for you.
Hoodzpah has a growing YouTube channel of helpful tips and tutorials, so be sure to browse the rest of their content. I'd love to see more designers release videos like this which are less than 3mins and get right to the point.