Rehearse and know your material. Be pleasant and brief. Don't even think about implying that there is a deadline or this is an ultimatum - in fact, it might be wise to say that you intend to continue doing an excellent job no matter what the outcome is. Time your raise request to come at the end of the interview. End on a positive note.
Good manners are always in style.
This is true even if you know that you are going to look for another job immediately. Leave on good terms. You may need a recommendation later on. If you don't get the raise, you have at least, exercised your option to ask. And even if you don't walk out of the boss' office with a raise in hand, you may have put the wheels in motion for one sooner, or larger, than was planned.