Listen to their ideas and give feedback. Feedback is valuable to an entrepreneur. Ask them to send you a link to their website so that you can look it over and maybe catch typos, give them feedback on the color scheme, font size, how it looks on a mobile phone, etc. If it is a book, tell them what you think about the cover design, during the design process – not after it is finished, that’s not exactly helpful.
Check out their marketing materials. You’d be stunned how many people forget little things like a phone number or email address. You can be the one to catch that and save them a bunch of money on reprinting their business cards and brochures. Give them a few minutes to practice their pitch on you and give them feedback on what they can improve upon, and praise on what is excellent.