Be a master of reading people?
They really want a buddy to fly with. I run a very, very small corporate flight department and when I pick someone new I have no shortage of guys who can fly the way I want them to. Everyone can handfly an ILS to minimums ATP standards.
If you've talked to these guys before, you should know how they dress. If it's a golf/polo shirt and slacks, then it is. If it's a suit, don't put on your men's warehouse 200 dollar special. Wear a suit you look natural and not overbearing in. I'd rather be underdressed and casual looking in slacks and a collared shirt than look like an 18yo in a cheap suit. Just my two cents. I'm sure by getting yourself in this position, you know more than any of us what they want.
I don't know any corporate flight departments that wear suits. Seriously.