1) Who is doing the most talking, you company spokesperson or your PR person? Should be the former, rather than the latter. Unless there’s something majorly going south in the briefing, a PR person should be seen rather than heard during the course of a briefing.
2) Hospitality: Sure, food is nice to have, but the best thing to have on hand during a one-on-one chat is a drink, preferably water. And this goes double if you are conducting briefings in Las Vegas, home of the dry throat and parched mouth.
3) Twenty-five minutes or less, if you please, depending on the topic. Unless you have some really juicy topics (note the multiple) of interest.