Most marcom providers will require prepayment of fees. All time spent ramping up for a project is considered billable time. Make sure that your provider has a conceptual understanding of your company, the technology, and your marketplace. Have them visit your Web site on their own time before the first meeting. Remember that provider who advertise or attend trade association meetings will recoup those costs in their fees.
Outsourced providers are a limited resource, often working simultaneously for several clients.
Make sure they have the bandwidth to take on additional work for your account and can meet your deadlines. Nobody will ever provide a bad reference, so trust your gut instinct. Marketing communications is an investment.