This applies to groups of two or more people as well. In a company, the guy who is in charge is the guy who has the biggest selection of things he can do. A typist or a mail clerk has a limited number of things he can do, and probably tight guidelines for how he can do them. But the boss or the owner can do something with any area of the company and he has a wide range of possibilities for how he can do it. That is why he is the boss.
In a processing session it applies as well. The party with the greatest range of freedom will control the session. That is very important, because one of our fundamental tenets is that the facilitator should be in control of the session. But she isn't, unless she is the most flexible person present.
A common school of processing advocates the idea that the facilitator must be bound by invariable rules for how she can behave. There must be one and only one correct way of acting in any given situation. The facilitator has a small number of choices to make and most of them are dictated by the behavior of the client or by the written instructions she received.
The only way that kind of facilitator is going to be in control of the session is if the client is subdued into being even less flexible. If we indoctrinate the client into only answering the question and doing nothing else, then it might work. Then the facilitator has a few more choices than the client and she will appear to be in control.
However, once the client or her sub-conscious gets wind of the fact that certain phenomena she demonstrates obligates the facilitator to act in a predetermined way -- then she isn't going to gain worth much. She will, possibly without knowing it, be able to pull the facilitator around by the nose. If she starts nattering the facilitator will ask for something she is holding back; if she says the incident is gone the facilitator will ask for a decision; if she states a realization the facilitator will end the process; if she says that she is outside her body the facilitator will end the session. In other words the client can operate the facilitator like a push button system.
It is an old rule that the facilitator plus the client together are bigger than whatever the client has to handle. Together they can deal with what the client couldn't deal with alone. That equation gets screwed up if the client finds herself in control of the session. If the facilitator starts being predictable then the client is pretty much alone in the session. There is not another thinking person there who can help her with whatever comes up.
You are needed in the session as a live, thinking person who is flexible enough to be able to deal with anything the client might come up with. That is the only way you get the client's respect and the only way you can deal with real live people. People are very different and respond in very different ways. You need to always be a step ahead and be ready for the differences.
There are rules for what you do in session. However, no rule is intended to stop you from dealing appropriately with the client in front of you. The rules are intended as tools, not as limitations or restrictions. There are a few limited ethical rules for what you shouldn't do, like you shouldn't judge the client or invalidate her or harm her in any way. Otherwise, what you have is mainly freedoms, tools, aids, guidelines, etc. You might be using many specific rules, but none of them are more important than being with the client and dealing with what is going on.
Don't teach the client the rules that you operate by. Teach her the philosophical principles, but not the exact steps of the techniques that you use. Don't put her in a position where she can sit and watch if you are doing things "correctly", or where she can predict what you must do next. If she gets to do that, she is no longer involved and the processing won't bite much.
A process facilitator is neutral in regards to the client's issues. However that doesn't mean that you have to be boring and formal all the time. It doesn't mean that you have to sit straight and stare stiffly at her all the time. If you have to do those things and the client doesn't, then it gives her control mechanisms an advantage. Be prepared to engage in any behavior that is necessary to stay in rapport with the client and to stay one step ahead of her in flexibility.
It is a good idea as a process facilitator to develop your behavioral flexibility. That is, the range of actions you are capable of doing. If you can act in many different roles, use different emotions, see things from different viewpoints, and you are in command of your own body -- then you will be better at being in rapport with any client in any situation without relinquishing control.