Unless physically barred from entering your property, the Assessor will always approach your home from the street it fronts on and knock on your door or ring the bell. If you don't answer, the Assessor will proceed to the exterior portion of the inspection (new photos, measurements, etc.). If the assessor has reason to believe someone is home and not answering the door, he will try other doors he comes across as he makes his way around the property to give you every opportunity to answer. When this is completed, he will leave the property, and that's the end of the process.
If you're home and you answer the door, the Assessor will ask your permission to enter your home for a few minutes to do a very brief interior inspection. 99.9% of the time, he will not photograph the interior of your home at all; the only exceptions are if your home features some rare or unique feature such as a movie theater or wine cellar; in those cases, only that feature will be photographed. The only purpose of the interior inspection is to get a general feel for the interior's quality and its condition relative to the age of the house. Once this is done, the Assessor will exit your home and conduct the exterior inspection before leaving the property.
Whether you live in a cottage or a mansion, a property inspection should be completed no more than 15 minutes after the Assessor steps on your property.