Usually the unsuspecting applicant attempts to handle the process on their own after their plans have been completed and financing approved. This is the wrong way to approach a construction project.
Long before you sign any contracts with a design team or a contractor or apply for financing you should be in talking with your local building and planning department finding out what the limitations are on the property where you intend to build or remodel.
There are many questions that need to be asked about the requirements for an approval of your project. You will want to know how long it will take to get an OK to submit for your permit. In some larger jurisdictions around the United States it can take as long as 2-3 months just to get an appointment.
Just a couple examples to clarify why. You will want to know if their are any environmentally sensitive areas on your site that you may not be aware of. The location of existing utilities and on site sewage disposal systems must be documented on your site plan.
You can find all this information about your local jurisdiction and their land use ordinances by clicking on this link. City Links.