Making sure the therapy works and continues to work for you.
During that first (and every other session) assess whether:
1. The therapist gets on with you
2. Understands your challenge
3. Seems competent, as far as you can tell, and
4. The session has helped you feel better
5. You can see a clear benefit from the session
If so, then, and only then, continue with another session. Many problems experienced by executives and professionals can be dramatically improved in one session; there may be no need for a second session.