Insouciance

There is a time to be laid back and cool but presiding a fencing match is not one of them. When you are a President there is no room to be casual; you must win the confidence of the fencers, the coaches and the crowd. They must believe you are in charge and that you know what you are doing. If you are not fully confident in your presiding skills then here are a couple of tips: Call halt confidently - don't um and ah about it.
Before you say anything, think about what you have seen (not what the judges or the fencers tell you). Then use the judges to confirm the situation (i.e. have any hits actually been scored?) Phrase clearly - the fencers need to know what you are saying, so point to the scoring fencer once you award a hit. This removes ambiguity. Point to on guard lines if that is where you want the fencers to start, or point to the exact place you wish them to come on guard if no point has been scored.
Be definite in your language. If you don't know don't give anything! Presiding is not a debating circle - you are in charge the other people are there to help you.
All these factors will help make you a more professional and respected president.