I redesigned the interior of a client’s house to incorporate a new full bathroom, the option to move their water heater inside the house, a dedicated computer station/home office, enlarged kitchen, larger TV room and more book storage. To minimize costs, the envelope of the house was not to change. I broke this rule slightly because one window in the kitchen had to be shortened to accommodate new countertops.
The project started by talking to the client about what they wanted. Next I did some rough concept sketches to see if we were on common ground. After positive feedback I measured and drew up the existing house since no blueprints were on hand. From there I modified those plans to provide the client with a few dimensionally accurate options. After a second meeting to discuss these drawings, I provided two refined concepts for final approval.
In addition, I taught myself the basics of Google’s SketchUp this week. Putting this house in 3D really helped me learn the software. There are still a lot of things to learn, but I’m happy to have generated something that is dimensionally accurate and useful even if some of the surfaces are screwy.
If any of you SketchUp masters out there have a link to a great house drawing tutorial, be sure to drop it in the comments. Lessons on how to use SketchUp Pro for house plans are worthless to me right now as SketchUp does not allow for direct import of DWG or DXF files (Why is this only a Pro feature?!).
Jason Patz 
I have a video walking through the new part of the house but I cannot directly host that on my site without additional cost. What is a good free place to put this 18MB AVI file besides YouTube?
The best way to learn is right on the job. I guess you are using the free version of SketchUp. I always start by bringing in a DWG floorplan and then extruding all the walls at once with Push/Pull tool. I guess they want you to buy the Pro version.
Try Photobucket.com. They give you 500Mb of free space for photos and video.
Charlotte and I used 3D Home Architect by Broderbund when we designed our house. It was about $10 back in 2003-4 when we were doing that. I’m sure the effects have gotten much more special since then.
There’s just no substitute for the virtual walkthrough. Sometimes I walk around our house and still remember how it looked on our computer.