How to shoot a sihlouette shot?

This is a little specific, but I have been asked to shoot a buddies wedding tomorrow, and one of the shots that I really want to get is a sihlouette shot of the two of them. What I would like is a shot with a beauitiful scenic background (outdoor wedding in a park near a lake, so not a problem), with the two of them in the foreground as a sihlouette. Can anybody offer any advice on how to pull this shot off? It would be VERY much appreciated.

Thanks!

Meter for the brightest part of the sky and recompose, that should do it.

put them in some shade, then meter for the sky and dont forget to turn off your flash *wink*

Just what I was thinking, thanks muchly guys!!

easiest shot is just put them in the church doors and shoot towards the outside. have them back to u , then face each other *click*, kiss *click*.