Look for reputable designers. There are hundreds of different builders out there and every single one has a different history and reputation within the community. If you take the time to check out all of the available designers, you should have no trouble finding the best in the industry.
Many firms offer pre designed plans that can be changed to accommodate individual tastes and preferences. There is a huge range of plans available online and from architectural companies - your task is sorting through all the various elements until you can narrow down a list of crucial components to be incorporated into your plan.
It is wise to speak to your architect about potential roadblocks in the project and about any other extras that are likely to be added to your bottom line figure. You may also want to discuss anything that your architect may think is a better design choice.
Plan your budget accordingly so that you don't get your hopes too high or settle for less than you deserve. That is, plan your budget based on what you can afford. If a half-million dollar home is in your dreams, make sure you can finance it - visit your accountant and bank manager beforehand so you know what budget you can realistically work with.