Ask the client what they are looking for. Use your smarts - don't shoot up at people on the alter, for example - you wind up with unflattering shots up people's noses.

Make sure to take photos other than formals. Formals are nice, but that quiet moment after the ceremony where they look at each other is nicer.

You don't say if you're the bride or the photographer - the advice would be better if we knew.

Make sure that you look at people before you shoot. It the father of the groom had a big hairy mole on the left side of his face, switch the bride and groom so that side is away from the camera. If you look before you line them up, it's much less embarrassing.