Anal Sex!..

Okay this is defiantly not my kind of thing and haven't ever tried Anal sex before, but my husband wants to try it on our anniversary. I am totally freaking out because I really don't want to, but I know he does and I'm willing to at least try it. I don't know what to do or anything about this! Please help me ladies! Is there anything I can do to make this less painful or more comfortable for me?