First of all, open up the photo you want to edit. Make sure to make up a backup copy of your original before working on it.

Here is what i'll be working with.

First, lets turn the photo in black and white, go to Image » Adjustments » desaturate.

Then apply some brightness/contrast to it, giving the image that over-exposed look. so go to:
Image » Adjustments » Brightness and Contrast. I set 20 for brightness, and +30 for contrast. You may need to adjust this slightly on your image though.

Now add some grains to the photo to give it the old look. Go to Filter » Artistic » Film Grain.
Now, for these settings, you can adjust it according to your taste, I set mine at:
Grain: 3, Highlight Area: 2, Intensity: 4

Next, add some of those old/brown look that you see on all the old photos, so create a NEW LAYER, and fill it with: #8A681B, now set its Blending mode to: Soft Light

That's it, Enjoy :)