The Ship of Fools website runs a Mystery Worshiper survey. Included in it are two great questions (here with answers from a visit to a church in Sydney):
Which part of the service was like being in heaven?
The choir was very well coordinated and in complete harmony. One of the best choral performances of Byrd's "Mass for Four Voices" I've heard.
And which part was like being in... er... the other place?
The deacon's painfully slow and soft chanting of the Gospel, which at times was completely out of tune. And communion was so rushed that the chalice was presented before one had a chance to consume the host.
Now, what if we used the questions to prepare our services and our sermons? That is, how can we make as much as possible like being in heaven and as little as possible like being, er, elsewhere!?