I (think) I used to hold to a view of the church which goes something like this: if you put your trust in Jesus, you become part of the invisible-universal-church. A local "church" (or "the local church", for some reason) reflects and points towards this invisible-universal-church. But local churches are nothing in themselves; the real deal is the true church, which is invisible and universal.
I (think) I now hold to a view of the church which goes something like this: Christ's ultimate purpose is to have this world populated eternally by his renewed, Spirit-filled people. But this isn't something entirely for the future: Christ has inaugurated this new humanity by creating a visible, identifiable, Spirit-indwelled, global community: the church. You enter that visible, global community through baptism, and you make it obvious that you belong in that visible, global community through continuing to trust Christ and to walk in his ways, and through sharing in the corporate life of the church, particularly through participating in the church's communal, family, covenant meal: the Lord's Supper.
I'm finding this new view wonderfully exciting, refreshing and biblical. It's been a gradual transition, largely driven by a growing awareness (with no little thanks to the likes of L'Abri, NT Wright and Al Wolters) that this world really matters to God. And, as such, the church's visible presence on the earth really matters too.
But this new view raises lots of challenges. On the first view, it's easy enough to identify "the local church" (even if it's not easy to find the right "the local church" initially!). And there's no need to think much more widely than that: you draw on the support of like-minded local churches elsewhere, when that is clearly helpful to the mission of your local church, but you can basically ignore everyone else. But if you want to think of yourself as belonging to a visible, global community (and not simply to a visible, local, self-sufficient manifestation of the invisible church), then it's no longer possible to be so selective. You need to (1) recognise the church, (2) identify with the church, and (3) relate to the church.
Briefly, here's where I am up to on those points.
(1) Recognise the church. Having come to a view of baptism as an outward, objective, visible sign, which is "the water rite of entry into the church" (Peter Leithart), it's pretty easy to recognise the church. In some sense at least (see below), it consists of all those people who have been baptised.
(2) Identify with the church. I really don't like leaving a church. Even though I've belonged to lots of churches, I don't think I've ever left a church, except through moving from one part of the country to another. But such a move has recently taken place, and I made a very deliberate move (back) to the Church of England. If you ask, "How can I best identify with the whole global church, while living in England?", it seems that the obvious answer is, "By joining the Church of England". It's the biggest and broadest church (or group of churches, or ecclesial body, or whatever) in the country, it has a pretty good claim to be the historic expression of the universal church in England, it takes history, tradition, "churchiness" and connectedness very seriously, and it has a fantastic pedigree in terms of relating to the wider, global body of Christ. And, reassuringly for me, it also has a great deal of life within it, and a strong, biblical, Reformed theological heritage. (See my post from last year about Stephen Neill's book, Anglicanism.)
(3) Relate to the church. Having said, in some sense, that all baptised people are part of the church, it then gets complicated. First, there are people who clearly love Jesus but haven't been baptised. That's simple enough: they ought to become members of the church by being baptised! But then there are baptised people who have drifted away from the church (not least the huge number of people who were baptised as infants, despite their parents having no connection at all with the church—people who have been baptised, but shouldn't have been baptised, in my view). And there are people who have been baptised, who remain active within the church, but who by their lives and teaching demonstrate that they actually hate Jesus. And there are people who belong to the church, but are not prepared to recognise large portions of the church. How do we relate to those people? I sense that it might be helpful here to look to Richard Hooker, the 16th-Century giant of Anglican theology and ecclesiology. He wrote about three kinds of separation: through heresy, schism or apostasy. These need to be distinguished, and handled appropriately. But I probably need to actually read some of what he wrote before saying more...