Will do a lot of the thinking for you. The best ones will do it without asking. This will be apparent immediately.
Will begin to bring value very early in the process.
Will ask questions you may not have asked yourself and do a lot of listening.
Will bring industry-specific knowledge or examples of companies that were once in your position.
Will generally charge very little for this information. Do not discount those that charge a palatable amount – too many good I.T. services firms have been used to formulate plans for companies that had no intentions of outsourcing and therefore ask that potential clients put some skin in the game.
Keep in mind that any good service provider (an accountant, a law firm, a marketing firm) will work to get a role in actually helping to write RFP if they want your business (another example of providing value early in the relationship).