It depends on the law in your state. A subpoena usually can be served by either a sheriff, a marshal or whatever name a court officer in your jurisdiction has, but often it also can be served by civilians, so called "process servers", sometimes it actually can be served by anyone except a member of one of the parties in the proceedings. It can be served in person, it often can also be served to a member of your household, left at your living place or work place and in certain rare cases even be served by registered mail.
Process servers usually know what they are doing, so simply pretending not to be you usually won't help.