I recently wrote a post about how I felt people were getting to hung up on noise (or grain) in their images. Personally I like a bit of grain in mine, especially the creative or conceptual themed shoots. It can add such an old world charm and nostalgia to our images and it’s not at all difficult.
I do love the old school almost Hollywood film charm it gives to my images. Often I find the images to me look more like old school film images. If you wish to add even more grain to say, black and white images, you can use the same steps, but add more grain or duplicate the layer.