I am enclosing a reprint of an article Mat Irvine did for Conrunner 3 which I hope you will find helpful. I also thought it might be worth telling you how a committee sees a Guest of Honour (though I obviously can't speak for any of the committees with whom you are dealing).
A Guest is seen in three main roles: as someone that the committee particularly want to meet/honour, as a "draw" for the convention and as an important element of the programme.
You will probably have already met some members of the committees you are guesting for and so there should not be much chance of misunderstandings arising through them being too over-awed to talk to you. (Media conventions have a lot of trouble with the "committee groupies" either monopolising the guest or being unable to communicate clearly what they would like him to do.) It is also possible for the guest to become the centre of a committee "feud" and being asked to lend support to one faction or other. My advice, in the unlikely event this happens, is to be above any such wrangle. Express no opinion on any aspect of the running of the convention that does not directly involve you.
As possibly the only professional at the convention, any press, TV or radio reporters will naturally seek you out. The committee may ask you to arrive early for this very purpose. All coverage of conventions tends towards the "Sci-Fi Loonies Beam into Town" style of reporting so it is worthwhile for a Guest to lend respectablity by speaking more of the literary aspects than the costume/UFO side the press like. In any radio or TV interview it is tremendously helpful if you mention the hotel where the convention is taking place so that listeners/viewers can come along. Another aspect of being a "draw" is to attract current convention-goers to this convention rather than another so the committee may ask you to write something for their programme book - a short story possibly - so that they can get collectors to come along just to get the story. It's up to you what you do about publication rights etc. but it is a nice gesture if you can manage to do it.
A guest provides a convention with guaranteed high attendence programme items, so there is a tendency to over-use him. John Brunner's rule of one major and one minor item per day is very sensible - and it helps if they are well separated. It is quite common for guests to be dragged away from meals because it's time to judge the fancy dress or such. Make sure you have at least two hours between any items. (Entrants in fancy dress competitions are among the most "bitchy" of fans so diplomacy in judging is very important - a good device is, after a check with the committee, to award extra prizes in made up categories to save offending the second place contestant of a close competition).
Most experienced fans will leave a guest alone in the bar or wherever as a matter of courtesy and new ones will be too shy to approach so it is often up to the guest to initiate conversations. I spotted Gordy Dickson sitting alone in the bar or lounge area of the Adelphi quite a few times at Follycon. If you are being bothered by an over-enthusiastic or boring fan then retire to your room to "work on your speech" and tell a committee person to rescue you if they spot you with that person again. A good committee keeps an eye out for this happening and knows the worst offenders.
I hope some of this is helpful and isn't teaching you to suck eggs.
All the best,