The variety of ways we lit the yard are some of my more favorite design elements from our wedding. It's kind of scary to think about lighting a large yard, but it ended up being fairly easy and cheap.
Because we were trying to conserve power for the DJ equipment, we knew we couldn't go overboard with electric lights. So we started with candles. Each dinner table had three candles in jars or other assorted vintage glassware. The dessert table was filled up with candles as well.
Since we were trying to keep people from wandering off into the depths of my parent's yard we created a border around the lawn by hanging candles in mason jars from sheperd's hooks. The mason jars were acquired off of Freecycle, but they were basically used peanut butter and pasta sauce jars. And we found shepherd's hooks at JoAnns Fabric for really cheap last summer (they were something like 75% off). We're going to use both the hooks and the candle jars in our yard this summer.
Since we figured most people would be on or near the dancefloor by the time it was really dark, that was lit a few ways. First, we had torches around the edge of the pool & seating area. In a big tree that overhangs the dance floor we hung up more of the mason jars with candles in them.
My parents already had lights strung up around their patio and around the hot tub deck/DJ area so we turned those on as well. And of course we had the floating candles in the pool and the fire pit, which I'm still on a quest for a picture of!
For the main part of the yard, we rented white lights. We were originally going to buy lights, but renting long strands cost us around $2/strand, which was cheaper than anywhere we could purchase them.
My cousin and P. dug small holes in the lawn and stuck posts in the ground. I've seen people use buckets with sand or some other thing to weight down the posts, but digging holes seemed more secure. He attached the lights to the poles and the house and that was it! I think we rented four strands for the yard. Each strand was attached in three places (two posts and the house).
This last picture really seems to show most of the different lighting elements we used. Nothing was glaringly bright, but it had a nice glow to it.