One of the most important things that you can do as a wedding photographer is to scout the location especially if it is outside. If you just go with the client to where they would like to take the pictures outside chances are that you will still get a good photo but it will take longer to set the client up in the poses that they want to get the correct lighting. But if you go before hand you can scout the entire location to find the best places to shoot the pictures at. It lets you get a feel for the location before the Client actually gets there and more often than not I have found that they will ask you for suggestions on where to take pictures.
As a wedding photographer many of the clients that I have had request to take outside pictures because they like the ground around the building where they got married or they already know that they want some outside pictures. The also happen to be some of my favorite shots because you can use either the sun or the moon as an additional light source and it can make for a really great picture. If you look at the picture above there is a great outline around the couple as they kiss.