What are my refinishing options for a concrete patio?
I have been researching this topic a lot lately.  I have even done a few test squares.  The Acid staining is awesome.  You should search for "acid stain" on Youtube.  There are countless ways to do it, so watch a whole bunch of those videos and you will get a get idea of it, and some good ideas of what you can do.  But here are the basics:


Clean the concrete. What is on it will determine what to use to clean it.  You will want to surface texture to be fairly uniform.  You can even put a thin layer of resurfacer on it to even it to hide everything.
Mask areas or put on stencil.  You can put about anything you want on it.
Apply the stain. Stain runs about $45-$60 dollars for a quart, but it will cover about 300 square feet.  The price may limit how many different colors you will want.
Neutralize.  This is just applying ammonia, or a more expensive neutralizer.
Wash the concrete.  Just Soap and water will do.
Apply Sealer.  There are a thousand different sealers.  You will need to figure out what kind of a sheen you want on it.