Understand your requirement and the rules of the "track" of acquisition you are in. Do not mix FAR Part 8 FSS procedures and FAR 15 procedures. If market research indicates your agency's need for services can be filled by placing an FSS order, stick to the FSS special ordering procedures and do not stray into FAR Part 15 territory. GAO will decide a protest based on the procedures you follow, regardless of what method you say you are using. If your agency need is so complex that you believe the FSS ordering procedures will not afford the opportunity to adequately evaluate proposals, then you may adopt more complex procedures ... but you should also understand -- and make sure others understand -- the time, expense, and risk associated with that decision.