I don't do any work in 2D anymore except for producing 2d documents. I design everything in 3d from the start. I really enjoy this method more than creating a 2d concept. My first step on any project is to model the site in 3d with all info projected on the 3d mesh - setbacks, easments, property lines, trees physically located etc. I then start modeling the home and immediately reference the home to the site. This way I always have a very clear understanding of the home design's relationship to site topography, features and boundary limitations.
It also helps me keep in check, height limitations. With the existing site modeled I also project a copy of the ground plane within the setback to the required height for the development - typically 28-35 feet. I save that geometry on a layer that I can toggle on and off while the massing of the home develops.
I've simply found this flow method works wonderful for me. It took me a while to break from looking at a home in 2 dimensions, but once I did, it was remarkable how quickly I could develop a design.