The words used in the dialog must satisfy both the business goals (including the company or organization image) and be meaningful and unambiguous to callers, so you need participation from business people and representative callers.
Before recording anything, act out the dialogs, using the “Wizard-of-Oz” technique, with one person reading out the application’s words from out of sight (say behind a screen or curtain), and another person acting the part of a caller. This avoids the need to write prompts and state tables before you have refined the design. Recording voice segments and writing code increases your reluctance to make changes, so try the live Wizard-of-Oz prototyping technique first.
When you are fairly happy with the dialog design, record the voice segments using the telephone, or synthesize them using text-to-speech. Recording over the telephone is easily done with either of two sample programs supplied with Blueworx Voice Response. To test the dialog, you’ll need to write prompts and a simple state table too. Start with company employees as the callers, and, when you are happy with the dialog, try it on potential customers or clients. If the service is aimed at company employees, start with experienced employees, but don’t forget to try it out on newcomers.
Only when you are satisfied with the dialog, should you invest in professional recording.