We should all heed this tip everyday, but it's particularly important on days you need to be sharp, assertive, and responsive.
Aim for something high in healthy fat and protein, that will be slow to digest and keep you from having sugar (and mood) swings in the lead up to the conversation.
I recommend two eggs, one piece of toast with butter, and 1/2 - 1 whole avocado. If that's not enough, add some meat of your choice, or maybe some almonds.
If you normally drink coffee, go ahead and have your cup (or two). This isn't the day to remove your daily cup of coffee if, for example, you may get a mid-morning headache without it. This is not the day to curb your caffeine habit.