Here are some tips:
* Curtains: Hang curtains to your porch, patio, pergola, or deck. Of course, you'll have to make sure that the drapes are made of outdoor friendly fabric, but curtains add a touch of sophistication and warmth when brought outdoors (not to mention they can easily hide any ugly features that you don't want seen).
* Furniture: Furniture placement is key in an outdoor area just as it is in your living room. Center a conversation area around a firepit or coffee table. Make sure you have comfortable padding or throw pillows so that your company will want to linger there. If you're planning an event with a large group of people, make sure that you have enough seating for everyone and group chairs around small tables rather than lining them up in a row.(Temporarily bring some accent tables from the interior of your home if necessary) This will allow manageable converstions between your guests.
*Lighting: (my favorite!) If you have an evening gathering on your patio or porch, don't forget the lighting. You can instantly change the mood of your party with beautiful lighting. Simple lanterns with candles hung on tree limbs or hooks on your porch/patio give a lovely glow. If you're uncomortable with actual candles, you can find many battery operated options-complete with flickering effect.
Landscape lighting is normally a part of landscaping, but add to it with some simple tiki torches (ncie to look at and also can keep the bugs away). However, some tiki torches can be tacky, so look for stylish iron torches for a more upscale look. They even come in sconce style torches!
A cheap and easy lighting solution is to simply add sand or soil to a brown paper bag (you can also cut patterns into the bag) and insert a tealight candle in the center of the sand. I like to space these luminaries approximately 2-3 feet apart for more effect.
Hurricane lamps or lantens with candles in small groupings of 3 or more are elegant. Don't space the lamps apart or individually, the grouping will create more impact.
Outdoor Rugs: Outdoor spaces are easily changed with the addition of an outdoor area rug. Again, make sure that the material is suitable for outdoor spaces and add one ore more just the way you would in your home: under a dining table, coffee table, etc. Choose a colorful pattern to break up monochromatic spaces.