i find my best support through trial, error and sheer quantity. if i try enough of them, one of them is bound to gel, sooner or later. in my own experience, support groups are more about the group chemistry the signs on the door or the theories behind the grouping. that group chemistry changes from one meeting to the next, so it pays to try the same group more than once.
My experience is it often comes down to the skill of the facilitator. A support group that is ostensibly geared specifically towards complex trauma patients can be a nightmare with a crappy facilitator, and a more generic support group can be crazy helpful with a good one.
I've always stuck with groups for trauma, sexual abuse or depression and mostly it's steered me towards good help for what support groups have to offer (primarily connection with other humans who 'get it', and secondarily to get help with coping skills - never to actually process trauma). The ones for trauma were, by and large, most helpful (private ones more so than the crap our public health system puts on, charity based ones being a complete roll of the dice, sometimes brilliant, sometimes terrible).
churches, schools, hospitals and community centers are my go-to spots to start asking. i just keep shaking the trees until the right nut falls out.
for what it's worth
personally, i prefer peer support groups which have no professional facilitator. i love the pro facilitated workshops, but the pro led support groups i have attended get stale in a hurry. just how much material can one person come up with? or? ? ? could just be my authority issues talking again.