Just RELAX...study. The ASA oral exam guide is great, so that's definately a positive. Our examiners in our area hit on some of these areas; loss of communications, airspace, aircraft inspections (IFR), ice and weather, decision making. Any decent examiner doesn't expect you to know everything, but you should be able to look it up. If you have spent some serious time studying, you shouldn't have a problem.
Good luck
papa t