There's a lot of talk about an Advisory Board.  Here are some thoughts about what an Advisory Board is/isn't, how to contemplate assembling one and how to compensate them. 

If I can give you one piece of advice about Advisory Boards I would say: 
HAVE ONE

1. Don't be chintzy on equity - give the equivalent of what you're (generously) giving senior engineers - maybe 25,000 shares or 1/2% to 1% of the (very early stage) company
2. Get somebody who's been through what Larry Rigby calls "The Agony of the Startup"
3. Find folks who complement your skills (but service providers "advise" the company as part of their arrangement, you don't need lawyers and accountants on your Advisory Board, you need business people)
4. Think about marketing and strategy experts, operational experts, folks who have sold their companies to a public company or taken it to IPO.
5. The kind of people you want will not want to jump into the "equity discussion" immediately, the best people will want to get to know you, see if there's a fit, and be excited about your business and opportunity.
6. But if there's a fit and you want someone to stay around and you're willing to take their advice, be quick to make a formal invitation to serve on your advisory board AND be quick to offer the equity.  Don't expect to necessarily negotiate this, just make a generously fair offer.  Great people should be treated greatly and won't be greedy.
7. Don't forget that Advisory Boards are not fiduciaries, so some people who can't/won't be fiduciaries can help you here.
8. Have regular meetings - but not overwhelmingly frequent.  If you're giving equity, once a quarter or twice a year could be excellent, coupled with regular interaction electronically or one on one with  Board members. 
   
9. Make the Advisory Board meetings  COUNT by understanding where you need help and being willing to lay that problem out on the table (preferably in advance) for some serious discussion and work.
10. BE PREPARED to  TAKE ADVICE.  Every good Advisory Board member will know that a strong, successful entrepreneur will not take all outside advice, but if you won't take their advice, why bother?