I've never seen that happen at any wedding I've attended. Usually people prefer to be seated early so they can have an aisle seat for better viewing. And then the ushers bring the guests in from the outer aisle so the better/closer seats are not forfeited.

I'm not sure if this falls under your "job description" or not since you're not actually guiding these people to their seats. Where are the ushers?

I think I would have the ushers approach the guests about 45 minutes before the service begins. Have them simply say, with friendly authority, that it's time to begin the seating. Without hesitation they should then start to ecort the guests in and merely ask whether they are guests of the bride of groom.

This happens frequently, particularly at churches and when guests haven't seen each other for awhile. I first tell the ushers that they need to get moving and take the initiative to ask people if they can seat them. Often the ushers don't seem to know what they are supposed to do. I then go to each group and tell them that the ceremony is about to begin and to please find a seat. I also have the guest book closed a few minutes early and I tell people standing in line that the ceremony is about to begin and they can sign it after the ceremony.

I wear a name badge when I am working and that lets people know that I am a person in authority and not just "Aunt Martha" telling them what to do. You might try speaking with authority; rather than asking them if they would be seated, tell them that you are about ready to start the ceremony and they need to be seated.

How about saying "The Bride has asked that people please be seated."

the relatives and close friends, who tend to arrive very early (1-2 hours ahead of time)

Wow!

Don't they have anything else to do?

This never happens in the weddings I go to in NYC, bcs these are BIG churches, and there's another wedding right before, so nobody shows up early.

Good advice here, though.

I agree w/the direct, non-suggestive approach. Tell, don't request. Polite tone of voice, and all, but an order nonetheless.

And "the bride has asked" is nice, too.

Thanks for the suggestions.

Sweet Pea, I especially liked your suggestions to close the guest book, to have the ushers approach guests, and to wear a name tag.

The organist can also give a huge hint that things are about to begin. Instruct him/her to begin playing something about 10 minutes before....or have the bride tell him/her that she needs to signal people that it's time to begin.
I also have never seen unseated guests be a problem, but rather the very early arrivers who are sitting in the church while the florist is making last minute adjustments and the wedding party doing some last pictures.
Linda C

I don't know why people show up hours early, but if they do, I don't blame them for not wanting to be seated then. 45 minutes sounds like a long time to me, too. I think most people stand around and talk for a few minutes before going in unless it is getting very close to start time.

Music is the best cue. Start it (or change it) when you want people to start being seated, and go around and just politely tell people, "Won't you please come be seated now?" A few groups ought to get the ball rolling. If they are not moving, approach the group that looks most likely to stand there forever and ask them to "help you" get everyone moving toward the room.