Many people have been asking how to get a sepia tone look in photoshop. There are several different ways, I will list the ones I do.
My preferred way: This is not the simplest way, but you have more control over the end result.
First desaturate the photo (shift + ctrl + U) . This will give you an image that looks almost black and white, but the color information is actually still there. It creates a warmer image than just changing to gray scale.next adjust the brightness (under image menu in the adjustments section). You will probably want to bring it down a bit. Black and white and sepia tone need to be a little darker than color shots to look good. After that punch up the contrast a little bit. Again, sepia and black and white both rely on contrast to differentiate "colors" to the eye. If your contrast is too low then the shot will lack depth and look flat. Next go to the color balance sliders (ctrl + B) and bring up the red and the yellow just enough to get the sepia tint you want.
method 2: the easiest way-
convert the image to grayscale (image the mode) then change it to duotone. Choose the color you want to add with the black, or loose the black all together and choose 2 browns. This is a very easy way to get the look, but I do not like it. Discarding the color information when you convert to graysclae really flattens out the image and even adjusting brightness and contrast levels does not help that much.
method 3: a different look
take your color shot as is and apply the sepia photo filter at 100 % to it. (image, adjustments, photo filter) This gives a hint of the sepia look but the most saturated colors in the shot come through, like green grass and red shirts. It is a different look that is fun to play with. You can desaturate the colors for a truer sepia look here.
There are many other ways to get a sepia tone look, but these are to me some of the easier ways and the first method listed is by far the best of these three and better than any plug ins I have used because of the level of control it gives you.
Any questions? feel free to pm me! I love to ramble!