If you're in the grounds of a hotel, the venue may arrange to have seating and even a red carpet to create an aisle, but quite often the guests will simply stand in informal groups instead (perhaps with a few seats for elderly guests). An outdoor wedding always carries a risk though - what do you do if the weather is bad? You might be lucky and get a day like this at Shieldaig Lodge in Gairloch a few years ago:

We certainly needed the sunscreen that day and midge repellent comes in pretty handy in certain parts of Scotland (north and west mainly) and certain times of the year (summer months) too! Don't forget wasp swatting season either - some people are seriously freaked out by wasps!
The following wedding of Kelly and John at the Roman Camp Hotel in Callander was another lovely day and the sun sparkling off the water gave the whole wedding a magical quality.

(This wedding was also videoed by James at Strageworx Productions and if you follow this link, you can see a web version of Kelly and John's DVD: http://www.strangeworx.com/kellyandjohn/)