Several folks have asked about model set-up and how to get started when moving from 2D to 3D and on into a BIM workflow. Here are some instructions describing how to set up a blank file and create layers, walls, etc. without the need for stories. There are two example/practice files that I highly recommend you "reverse engineer" the wall styles, slab styles, etc. so that you can see how the offsets work, etc. Also, read the instructions all the way through first.