Textures and Lighting. one of the best things I learned early in 3d. Take a cube throw it into the scene. Now, make it look real. play around. now make it look real but on a table, or peice of cloth. play with shadows. look at things on your desk and see how light plays off things, what textures look like. things aren't flat and dull (well most of the time they aren't). People don't look like plastic barbie and ken dolls. nothing wrong if ya want them to look like that, but if you want photo realism they need skin that, well, looks like skin. postwork if you know how to paint or draw in a 2d package can add a lot to your renders too. can depend on what your trying to acheive also. Play, and MOST important, really can't stress this enough, have FUN! Welcome to the show, it's a wild ride :)