Design And Draw Your House
Do the house design yourself
You could decide to pay an architect to design your house, but I very much advocate doing it yourself. It's a lot of fun and probably a once in a lifetime opportunity. The other reason not to use an architect is that the architect will not be the one that has to build it. It really focuses the mind on producing an easily buildable cost effective house if you are the one that will be building it (and paying for it).
There's info on house design here .
Start with a simple app
Change and change again
The process of designing your dream house is a very iterative process. You need a really simple way to plan things out and then change them and change again. Drawing floor plans and elevations on squared paper is what a lot of people do, but this is no good because it's too hard to change. You need to be able to select a wall and drag it a bit to the left. It needs to be a vector based drawing app on a PC. AutoCAD is a very powerful vector based drawing program, but it's expensive to buy and can be difficult to use for rapid drawing and modifying. There are various simpler vector drawing apps to choose from, but in my opinion the best free one is the one that comes with OpenOffice called "Draw". You can download it from http://download.openoffice.org/index.html . I set it up with one dotted line grid square representing a foot, but with the ability to move things around to snap to an invisible 6" grid.
Eventually you will need to produce drawings using AutoCAD, but at least you will have most of the detail of the house design figured out before-hand.
Use someone else's design as a starting point
You can use my drawings
It's easiest to start with the drawings of someone else's house and then modify them to meet your needs. That way you don't have to setup the scale yourself, and also you can just drag other people's shapes around such as toilets. You may want to get the drawings I did for phase one of my house. They are available by sending email to the email address given at the top of the page in the header.
Accuracy is important
You cannot cheat with the jigsaw puzzle
Even though you'll only be using a 6" resolution in your drawing, and even though these are not the official blueprints you will be submitting to the planning department, you will want to size things accurately. Fitting all the different internal components of a house together is a jigsaw puzzle. You cannot cheat by drawing the stairs smaller than they actually need to be. If you do things right then there will not be any significant design changes needed when your drawings are converted to the official blueprints.
A small change has ripple effects
A small change on the positioning of things on one floor can mean the stairs move a bit and that will cause changes on other floors. You really are dealing with a jigsaw, and it's a 3 dimensional jigsaw puzzle. When you change one of the floor layers, make sure you properly update all other affected drawings to keep everything in sync.
Think about structure
It's less costly to build an inherently sound structure
As you do the design, try to avoid doing anything that would cause unnecessary weakness in the structure. Obviously you will want to have windows and doors, but every time you add one, try to imagine the effect that will have on the forces within the walls. Imagine building a cardboard model of your house and then put a lot of weight in the attic - would the cardboard model crumple and fall down? Obviously the answer is that with enough weight it will fall, but try to design to maximize the amount of weight that it would be able to support.