In general, I prefer to meet with both partners starting with the first session. That way I can hear both points of view and see the relationship in action. Sometimes one partner asks to come in alone first to see if I am the right fit; that is OK too. But then the other partner will have the option of meeting with me alone for a session too. It is very important to be fair and even handed.
Although the bulk of our work will be done with both partners in the room at the same time, sometimes I may request an individual session for strategic reasons or you may request an individual session for your own reasons.