I'd really like to assemble a Board of Advisors, but I'm not sure how to start. I've found that being kept accountable to someone or a group of people can really serve to meet business goals. Should I have an organized structure for people like this? Do they have to be in my personal network for them to be willing to help? I'm thinking I want to aim high, and have those that are more compatible with who I want to be rather than those that are immediately accessible in my existing network.
Peldi from Balsamiq Mockups built a nice board of advisors. He explained how he did it (even with the actual email template) and how it's working out for him in this interview with him.
To directly answer, usually they'll be in your network, because "advising" is a significant time investment and strangers are unlikely to want to do that.
Aiming high is good, but consider starting with some more accessible folks, and then approaching others once you can point to a few other people who are already on board.
Disclaimer: helping companies create a board of advisors is part of what I do for a living.
First of all, congratulations on recognizing the value of setting up a board of advisers -- many entrepreneurs give little thought to this incredibly valuable resource.
Next, allow me to respectfully demur as to some of the other comments by saying that an ideal board of advisors is likely to be from outside your network. Advisors are quite often very highly placed in companies you would never dream would be interested in your little venture. And that's true: the company may not be interested, but the specific individual just might. Senior executives often have an entrepreneurial itch that is not being scratched in their normal jobs. Your advisory board provides them an opportunity to stretch themselves, and gives your venture an opening to form a strategic partnership with a company you could never have reached otherwise.
Which takes me to my next point: the best strategic advisors are connected, not necessarily to you, but to the companies with whom you'd like to partner. Note that I say "partner" rather than "sell to": the advisory board is not a great place for prospects or customers (although a separate customer advisory board is a great resource as well). Through his or her participation in your startup's advisory board, the advisor will get to know you and your company, and the odds of putting together some kind of strategic deal with the advisor's company are greatly enhanced.
Because the ideal member of your strategic advisory board likely comes from outside your network, it is often advisable to use a third party to make the approach. And that is the only self-serving comment I will include in this response.
Finally, it is important to distinguish between your advisory board and your board of directors. It is very unlikely that an advisory board member would ever become a director, unless you end up doing a merger or equity funding with the advisor's firm. The requirements are just very different.
What I think I'm seeing emerge here are two schools of thought. There's the "Jason/Balsamiq school," which favors a very informal advisory board comprised primarily of people you already know and admire. Then there's the "Scott/Warrick school," which favors a more formal organization, assembled from industry veterans with specific connections or skills that might be of value to your company.
Do you guys think that's a reasonable observation?
In the end, it's going to be a function of what you're comfortable with, and what seems to you to have the most value. I also don't think they're entirely mutually exclusive: you should always be able to go to your network for advice and support -- that's what makes them your network! That doesn't rule out the creation of a structured advisory board at the point at which you are comfortable moving forward with it.
If you're not that well connected, you might consider collecting a more informal group of advisors - perhaps people who can be a simple sounding board for you. The best sounding boards I've found were just mild acquaintances who I found to be incredibly like-minded (though this doesn't mean they always agree with me) after some conversations. It's a start and through secondary or tertiary contacts, you'll network and find the kind of people you're looking for - connected, deep pockets, that sort of thing.