This possibility arises of starting a group when there are so many independent and liberal movements today. A growing movement is the Progressive Christianity Network, and then there are Sea of Faith Groups. Both are still thinly spread, but clusters are appearing. There could even be liberal religious groups like church fellowships. I have looked into a range of them, in asking why they cannot get together, and looked at even those where some get ordained and consecrated via several lines of apostolic succession - producing their own small religious communities like churches. Then there are simple discussion groups (talking, reading) or perhaps activity groups (practical or spiritual).
However, if the people starting such a group are already in an existing one one, like a church, then sensitivity is needed. If the group forms inside the church, it may look as if it is a potential takeover, or defensive, or against the ethos of the church (if opposite or mixed), but if it forms outside it might be seen as competition, schismatic and divisive.
Sometimes a group may have the active support of the minister and leaders, or at least an understanding. The degree of attachment the group has to church depends to some extent on the absence of hostility from minister and other leading people.
Also it may involve connections with more than one church, and more than one minister or ministers of one denomination. Conversation routes may then be very complex, a multitude of sensitivities and motives (real and imagined) arise, and keeping channels open may be quite complex. For example, some in one denomination may ask if a group is a front for another denomination and wonder who knows most about what.
It could be that the greatest need for a liberal group is in a locality where the local church simply does not incorporate the liberal aspect within its walls. If not then setting up such a group will be unattached to that existing body.
So how to do it: well a group should have a clear, specific, public agenda (the constitution can be more general or imported). It should be launched in public in an open meeting that all who want may attend. The group should at least be semi-detached if not detached from an existing church or churches but someone answer questions about its progress or otherwise to a church body or bodies as a matter of courtesy and openness. It is still worth keeping channels open in the face of local hostility whilst defending against actual disruption.
Starting a specifically liberal group is a challenge to some people who doubt the legitimacy of liberal religion. This is why they are wanted! Such a group is seen often as undermining, or a cop-out, or shows (say, to evangelicals) an evangelistic opportunity that the liberal people simply reject. Still one can be open about its purposes and what it is doing.
What cannot be compromised, once it is set up, is the agenda of the group, its intellectual and other sources and its intentions. Disruption is not permitted, even if questions are and there is space (for a time at least) for oppositional points. Nor can there be restriction on its appeal for new members from outside, on a liberal basis of contribution and not people to be 'evangelised'. A principal need is a safe space for people to express doubts, to formulate faith alternatives, and think things through in different ways. The group decides, not others, whether there is any value, for example, in 'upholding the Incarnation' or what understanding, if any, is given to resurrection or other doctrines, or how far to incorporate the insights of other faiths and philosophies. It decides how faith is to be understood, or (more likely) the degree of active toleration given to individuals to give different views.
It may be that a church already has a discussion or some form of activity group. There may even be a liberal hue to it, as another group in the same church may have a Catholic or evangelical hue to it. Good, but such an internal group can never simply become one of a liberal agenda (unless this identifies the church). Such a group must always operate to a wider ethos of the church it is in. It may indeed be obliged to uphold certain doctrines or dogmas in some public manner.
At some point the new group may want to sign up to an existing network, or have an association or membership. Then its ethos becomes drawn from that body more obviously and completely. It would be a case of keeping good relations with others where it built good relationships (if it did).
Groups go through highs and lows. One important matter is not to think that the world can be changed. A discussion group is just that - it talks. There is no point saying later, "Well nothing is being achieved." It is if people are talking. It may help to read, or share the preparation of papers. Be a seminar! A group that worships is the same - it succeeds if it worships. A group that does practical action might have to be more ambitious in the doing, and even more ambitious is wanting to achieve combinations of these. Matters should be kept simple and achievable.
Another useful characteristic for a successful group is to have a historical root. This is to say, know where the present is and future direction according to what was the case. Blog entries on religious groups previous to this one (below) are all about sources and connections.
It is a frustration when people are 'not on the same wavelength'. The liberal group (like many another) sets out to achieve this. It can draw on many more sources than of the one denomination, and can say things that might frighten the horses elsewhere.
It may achieve a safe place, even a forward-going place, if it is under pressure in the religious situation in a locality. In such a situation, so what if it became a congregation? It offers actual choice. If this happened where there was no such pressure in the locality, then it would be a failing in one or more local churches to have such an extended new development beyond. Such a situation would not come about where the people who set up a semi-detached group are already catered for within that church; it is just that in their added group they can specialise and go beyond provision.