1. First create a diagonal scanline pattern. CTRL+N to create a new canvas, select 3px by 3px. Zoom in so you can work on it easier. Make sure this layer is transparent.
2. Select the pencil brush and draw our three diagonal points, corner to corner.
3. Go to edit, and define pattern, name it whatever. Close the canvas now.
4. Open up the photo you would like to add the vintage effect to. on the top toolbar, select Image > Adjustment > Hue and Saturation. A box will appear. Check the Colorize box, and then you can adjust the colors as you like. We will try to give it an old brownish color just like the old style vintage photos. Use settings like mines. You can go back in and adjust the details later.
5. Right click on the image layer and select Blending options. Go down to Pattern Overlay and select our scanline we made earlier. You can adjust the opacity however much you like. I find that 100% looks too much so i toned it down to about 30%
6. Create a new layer. color it #483029 or a similar shade, could be black or white or anything that fits. Now go to Filter > Texture > Grain > Vertical. Set the scales to however you like.
7. For layer options select lighten.
8. You are done, you can go in and add more stuff to it. I will add a character to it but leave it in color so it stands out. A very subtle tutorial but a nice touch. I also used this site as reference.
Click to enlarge