You need to know that your inspector will cover all the bases for you, and he needs to know that you do not have unrealistic expectations of what he can do for you. The ASHI Standards of Practice were created so everybody involved will know what a home inspection can and cannot provide. I strongly encourage you to read the standards before your inspection. http://ashi.org/inspectors/standards/standards.asp
As a member of the American Society of Home Inspectors (ASHI), I adhere to ASHI's code of ethics as a home inspector. The code of ethics can be viewed here: http://www.ashi.org/inspectors/ethics.asp.