there are also many other factors that you must take into account:

mapping over modeling, if something is farther away and can be mapped to look 3d then you can save poly's
----alpha mapping huge help when it comes to this


boards: as before mentioned, the importance of a char/sprite that is far away can be put on a camera facing board for good measure

hidden face deletion, if you cant see it on camera in your game... delete the face (helps in long run)


last tip, by this book: Creating the art of the game by MAthew Omerick this book will have a lot of usefull information