Whether they're speaking at a conference, networking or being on a stand at an expo, do these things to maximise their chances of success:
🎤 Give them permission to fail. "I know you'll do a great job" may create unhelpful pressure. Instead, tell them "I'm happy with whatever happens, because you're a brilliant expert and I love how you talk about your subject". Make them feel like a complete boss and they're more likely to relax (and consequently do a great job!).
🎤 Let them know that you've got their back; you''ll tackle any challenges like unpleasant higher-status people if you can ('Oh, he's always like that - drives everyone crazy. Don't sweat it'). Make sure they know they're off the hook for their day-to-day responsibilities (they won't have to check their email) and that you'll feed them vital information if necessary so they can focus on their task. They may feel quite alone, so send them an encouraging message or two, especially if they've had a good mention on social media.
🎤 Go through all the day-to-day practicalities beforehand: how they'll get to the venue, the format of the event, where they can get food/water/tea/coffee, where the toilets are, what they should probably wear (for a good temperature, to be able to move easily, to stand all day without hurting your feet, wearing something you can attach a mic to etc). Sorting out everything to make them as physically comfortable as possible will help them feel as mentally relaxed as possible.
Every speaking engagement should have this relationship.
Good luck out there!
(If you're the speaker and the boss, then you play both roles: 'M' when you're preparing, 007 when you're at the event.)