This is a really simple instructable. You only need a tree, a rope and your own hands.
WARNING: look out, some trees are not strong enough!
Everything what you need is:
1. A tree
2. A rope of 4 or 5 meters
3. your own hands
Step 1: Step 1
Make really much knots on one place so that you can sit.
Step 2: Step 2
Make a knot on the height of your hands. now you have a knot for your hands.
Step 3: Step 3
Knot it on a tree and swing!