Garden seating can vary from formal to informal. Choose seating to fit your setting and fill your needs and the needs of guests. Consider whether your guests require cleanliness and comfort or a more natural, tactile experience. For location, face your seats toward the more comely features of your space--a corner filled with flowers, the sweep of the lawn or a small grouping of bird feeders. This will give your guests a lovely view or entertainment in addition to relaxed enjoyment of the space.
A fallen or downed tree makes a comfortable and informal spot where those touring your yard and garden can rest. This type of seating serves more than the human visitors to the area. Allowed to naturally decay in place, a fallen log can act as a miniature ecosystem, providing a home for any number of organisms. Trim back branches from one side or trim them away from a relatively flat section to give access to the trunk. Strip the bark away or allow it to remain in place and fall away on its own as the tree decomposes.
An old-fashioned board swing for adults or a tire swing for children provides whimsical informal seating. Landscape contractor Roger Cook of This Old House.com recommends using a branch at least 8 inches in diameter and locating your swing at least 3 feet from the trunk, but not so far out that weight on the swing stresses the branch. The swing should have sufficient space to move freely along its path without encountering an obstacle. Bare grass or soil serve well for footing beneath the swing.
For comfort and mobility, consider lawn chairs. These are often made with metal frames. Inexpensive lawn chairs have nylon webbing, while higher end pieces come with cushioned seating and weatherproof fabric. Tilting your chairs against a table or tree while they are not in use will ensure they are handy, close to where you use them, but keep the seats free of bird droppings and relatively free of rainwater.
Formal seating may involve a heavier, more substantial piece like a marble or stone bench. These are long-lasting options which retain their appearance well and stand up to the elements. They can be easily cleaned with a nylon brush. Stone benches provide a cool place of repose on a hot day. Place the benches in full or partial shade for the comfort of guests.