The usual format is for all of the people who want to ask Forrest a question to take turns doing so once he arrives. Ideally, each person would be able to ask whatever they want to ask fairly succiently. Once all of the questions have been asked, then Forrest will respond to the collection of questions as best as he is able. For various reasons, it may be the case that not all questions that have been asked will also get answered.
Also, be aware that frequently there will not be an opportunity for follow-up, so be sure to ask what you need to know at the beginning.