If you’d like some insight into how it’s done, this essay at the Catholic News Service is both informative, and inspiring. The pastor, Fr. Kenneth Doyle, concludes:
There is still, of course, some sadness over the merger and some adjustment yet to be made; it is not an easy thing to give up the place where, for years, you have known peace; where you were baptized and married perhaps; the church from which your parents were buried. But there are no public protests, no sit-ins and a good deal of enthusiasm for celebrating an enthusiastic liturgy in a full church. (Our average weekend attendance a year ago was 1,295; this month it has been 1,548.)
Much of that success is due to the two-and-a-half years of diocesan planning, with representatives of each parish meeting in clusters to suggest the new configurations and the bishop accepting virtually each of their recommendations. But the rest of the success is due to the resilience of Catholics who view things realistically, who adapt flexibly and who value their faith far more than their buildings.
Read the link to find out how they did it.