The point of advising is to have fun but it's also to align with the upside of the business. So the things to consider / ensure are.
- Are they venture backeable ... if they don't plan (or you don't see them being able to) raise venture capital, then being a formal advisor (with equity) won't matter.
- Do you trust them. As an advisor, you're extended your brand and credibility to the team so you need to ensure they'll be good stewards of it.
- Are they coacheable ... when you talk, do they listen and are open to the advice. Do they take action?

As for compensation & commitment, here's what's normal.
- 0.1-1% equity in the early stages .. usually over 2 years vesting monthly.
- You make yourself available for 1-2 hour per month, and help throughout making introductions, reviewing documents,etc

Personally, I think it's super important to ensure you tell what you won't be doing. Ex: I won't be accountable for a work product, as in - I'm not going to run your marketing / development team :)

You never know what people expect, so it's best to discuss it upfront.

Also, if you plan on doing formal advisory (for compensation) - it's ideal to get atleast 10+ companies to help out in that format to ever see a financial return ... your essentially acting much like a VC.

So just understand, there's a very high likely hood that it won't go anywhere financially .. but it can be super rewarding.

The key is that you enjoy spending time with the team and learning about their journey.

I've served as an advisor to a number of startups, both in formal accelerator / incubator programs, and on the advisory boards you are describing (not to mention the free advice for friends and family).

It sounds like you've already decided that you want to do it, and you're just looking for potential red flags or pitfalls, so I'll skip the pitch on how rewarding it can be, even if it doesn't "pay off".

Factors to consider:
1. Companies pivot. Founders rarely do. Focus more on the who than the what, because the idea and model might change drastically over time. It's important to like and trust the people you'll be working with.

2. How do you fit with the rest of the advisory board, and is that important? Some entrepreneurs like their advisors to meet and work as a group, while others deal with their advisors very independently. Know what style and what type of team you're signing on to.

Questions to Ask:
1. "What do you expect from an advisor?" You'll get a lot of different answers from different entrepreneurs - make sure your expectations are aligned. Talk about the important things like honesty and accountability, as well as the potential frustrations like responsiveness and scheduling expectations.

2. "What skills / knowledge / experience are you looking for in me specifically?" I might think I have a great marketing mind, but if the board of advisors already has a marketing expert, they may only be looking for my technical knowledge or relationships. Make sure you don't think you're bringing something to the table that isn't what they're looking for.

Lastly, in terms of the deal structure, be honest if they make an offer that you feel undervalues your time and / or experience. Steer the conversation toward opportunity cost (If I commit to you, I have to say "no" to other things that require my time) - that simultaneously demonstrates that you know your value and that you intend to abide by your commitments.

Compensation, time, commitment, and will your input be valued. Lastly, will you be proud of the outcome/company and will it help you with your future.
Don't stop taking massive action.
Best of Luck,
Michael T. Irvin
michaelirvin.net
My books are available exclusively through Amazon Books. Check out my book "Copywriting Blackbook of Secrets"
Copywriting, Startups, Internet Entrepreneur, Online Marketing, Making Money