Which FSDO are you doing it at?

They may break out the the aircraft maint logs, so make sure you know what is in them. When was the last 100 hour? When was the last pitot static certification? Is the transponder current? Things like that you've probably never thought about. Be ready to prove that the a/c is full up.

As far as the oral goes... I did mine at the MCO FSDO, notorious for 6+ hour orals. We were done in under two. When all was said and done I asked why I had heard all the horror stories for mind numbing oral exams. The inspectors basic explination is that most CFI applicants are hair triggered to give lengthy technical answer, which just digs their own grave. Pretend like you're talking to a 5th grader. When they ask "what is a stall" answer with "the point at which the wings stops producing enough lift." If you get into boundary layer seperation, critical AOA, etc you open yourself up to follow on questions. Bottom line, your answer should be very basic, and not create any other questions, but at the same time give a complete answer. When you're driving around town, ask yourself questions you think they may ask in the oral, and then answer them. Then go back and think about your answer. Are there more questions that could be asked from my answer? "What is p-factor?" The left turning tendancy created from the decending blade creating more lift than the acending blade. Asked and answered... if he wants to go further then yeah, you'll have to explain why, through AOA, etc., but the bottom line is you gave an answer anyone would understand.

As far as the practical, make sure they are doing EVERYTHING! I almost got nailed because he didn't throw the prop full forward until the turn from base to final. On the climbout he asked for a debrief on his (whatever the landing was)... when I talked him through everything he asked "is there anything else?" I backed up my debrief of it a little further beyond just the landing to doing the gump check on the downwind, and he told me had I missed that we would've been done. So again, let them make the mistakes (like a real student would) and save the learning until after that event is complete. Just like a real world student they'll pretend like they're becoming over loaded if you never stop talking. They may or may not ham fist the plane too, to find out where your threshold is for taking over.

Just be confident, prepare, and look at him as if they were your first private pilot student that doesn't know anything.

Let us know how it goes.