If your designer does not completely understand what you want, he may create a design that does not work for you. Having your plans repeatedly changed and redrafted could add considerable time and expense. A small detail, such as a few inches difference in bathtub dimensions, can sometimes cause a chain reaction, requiring the redesign of the bathroom, adjacent closet, nearby stairway, upstairs bedroom, and so on. Lastly, it is best to do a Cost Analysis before the plans are finalized. If the estimated costs are too high, sometimes the budget can be increased, but often the design must be altered to fit the budget.
People are different.
Some have no trouble envisioning their home from plans, for others it is nearly impossible. There are ways your designer can help you. Have a model built. Go to the homesite and use stakes and strings to roughly mock-up the floorplan on the site. Post a large copy of the proposed floor plan on your wall.