Good models, textures, and lighting only goes so far. What a lot of people forget about making CG look real is that there are imperfections in the photographic process(digital or film) that just aren’t there in rendered CG. Cameras and lenses have a limited depth of field, there is an atmosphere through which the light moves, etc. A lot of this stuff is subtle and we often don’t even realize that it’s there until it isn’t, and then our minds scream “FAKE!!!” and we don’t know why. A good habit to get into is to use reference materials of the kind of thing you are looking to create. If you want to make a car, then look at how a car looks, look at how the light hits and interacts with the paint, how the glass on the windows has a different kind of shinyness to that of the paint, or the wheels, and so on.
Beyond that, well, a lot of the tricks and techniques that can be used to make something look photorealistic are very dependent on just what it is you are making, so I couldn’t tell you much more.