Many clients can and do decide to manage this process independently of consultants. The most important thing is to get your decision-making team in place as early as possible. Very often clients underestimate the time and effort required to complete a successful pitch process. We would strongly advise that key diary dates for your company's pitch team be agreed and blocked-off as soon as possible so that your key decision makers are available and present at the vital meetings throughout the entire process.
A mutual non-disclosure/confidentiality agreement (NDA) ought to be signed before undertaking any meetings. It is of benefit to both parties to enter into such an agreement, which should cover information and materials supplied by you for the pitch and those produced by the agency in response. IAPI have model NDA templates for agency and client use available from the pitch pack.