1) Create boundaries. Whether you use the house, an outside structure, a fence or even trees, try to separate this space from the rest of your yard. Working with the architecture of your home and yard, you can carve out a space. Using potted plants helps create the illusion of walls, especially when plants are on trellis or obelisk structures.If you have a budget, hang a sail cloth 'roof' or even outdoor drapes. Define the seating area with hardscape like gravel, pavers, or a rock border, or simply lay down an area rug. Many stores sell easy-to-assemble decking that locks together creating a patio. Using polypropylene rugs is ideal for outdoors, but a covered area can tolerate sisal, cotton or other blends. Trees and plants can serve as your boundary and can be enhanced with string lights and sheer drapery. Umbrellas are handy 'roofs' and serve as a place to hang lights.
2) Add light. Candles are the simplest way to bring light to outdoor rooms. Iron stakes with candles under glass holders, torch-type lanterns, and hanging candle lanterns are all easy to find and use. String lights - especially those with decorative globes - can be hung from trees, the trellis, or even from yard stakes and install quickly to provide instant, warm light. If you have a structure, consider installing an outdoor rated fixture or even a hanging iron candelabra. For tabletops and to light the paths, use hurricanes with real or flame-less candles, candles in jelly jars, and floating candles in dishes. Consider safety first in what you choose.
4) Soften it. Using fabric - pillows and seat cushions - will make the space cozy, even if you opt for plastic stackable chairs. Sun resistant fabrics are easy to find in ready-made cushions and pillows. Handy at sewing? Your fabric options are almost endless and you can customize the style and patterns. Use tablecloths and colorful napkins to dress your table; cotton is easy to wash. The sight of a covered table is inviting and you can customize with fabric remnants, layered or used one at a time. Skirt a bench for a dressy look. Hang drapes where you can. Polyester sheers are inexpensive, and even if they are used in a non-covered area, may be able to be washed and re-used. On partially covered patios and balconies, I use cotton or cotton-linen panels that are easily taken down at the end of the season and used for years.
5) Bring on the decor. Add decorative elements as though designing your indoor rooms. Hang iron elements on a wall, from a tree, or even from a stake. Glass hurricanes look wonderful filled with findings or just candles. Colorful or monochromatic ceramic bowls, vases and planters will make the space look finished and may also be used for food, flowers or just decoratively. Tables look great with centerpieces so be creative in what you use. I have a plant stand that I layer with plates, and fill the plates with seashells, candles, or plants (!). Baskets work well to store items like extra pillows, a throw, or magazines and books. I have a lidded basket that's large enough for seating, and topped with a pillow, becomes an extra seat. Ceramic garden seats add color and a place to sit. The iron pieces found at some import shops, serve as tables, planters, and even a place to store candles, flashlights and big spray.