Summarize:

In general, you'll need a space that's about 1415m (4649ft) for your horse. This will give it enough room to trot, but not so much room that it will feel like it's out at the open, which might make the horse try to escape. If you don't have a ring, try using bales of hay to make a circle instead. When you're handling the lunge rein, take the time to fold it neatly in accordion-style pleats. Folding the reins will help keep any excess from getting tangled, and it will make it easier to hold. Never fold the coil the line around your hand. If the horse bolts, the line could pull tight around your hand, causing you serious injury.
Bring the horse into a ring or an enclosed pasture. Fold the excess lunge line back and forth on itself and hold that in your hand.