You should pay them in the form of referrals and connections through your network. Also a small amount of options/warrants are always nice, but you need to make sure that they are adding value in exchange for them. As far as formal payment goes, I would run from any advisors that require it. Once the business is starting to gain some cash flows I would suggest holding a quarterly dinner at a decent restaurant with the entire board present. As busy as advisors are, placing them in a formal atmosphere with the rest of the board usually requires them to slow down for a second and actually focus on you and your business.
My 2 Cents.