Admitting unknowns and handling imponderables

Question about the top three pitfalls to watch out for when you start using apologetics in conversations with others.  

• What are the top three apologist pitfalls—i.e., if you’ve just read Tactics, you’re ready to go, and Jehovah’s Witnesses show up at your door or your atheist coworker starts asking you about God, what are the top three things to watch out for?