The following post about 3 ways to DIY your Chroma Key was made by Ben Eadie of DVRebelGear.com.
There are several ways to get a decent chroma background for a photo for the DIYer and the results are just as good as any pro system I have encountered. We will cover 3 solutions I have used with great success and all cost less than $15. You can use a green sheet, you can paint a wall and you can make a pop out chroma key like a pop out reflector. I use green for my key but you can also use blue if you choose.
First here is some advice on getting a good shot on a chroma key. Never use an on camera flash. Make sure your object is far enough from the screen to not pick up any green reflection off of the fabric. Your object/subject should not cast a shadow on the key. Avoid shiny things (note the top of the table in the examples below, they all have a green reflection in them because it is a slightly shiny surface) I make sure that I have things a minimum of 3 feet in front of the key. Last make sure you have an EVEN soft light on the chroma color. The more even the light on the key the easier it is to edit later on in your photo editor.
First, the green sheet. You can get fabric sheets at your local WalMart. Get a green that looks close to the green in the pictures below. Or you can even get the fabric off of internet stores such as http://www.joann.com (get the Symphony Broadcloth in green here) Now this is as simple as hanging it on a wall with tacks.
Advantages: Super simple, easy to move and store, can be draped over things to key out later, cheap and easy to replace
Disadvantages: Wrinkles easy, sometimes hard to hang
Second, if you have a wall available to paint then go to your local paint store and get some flat latex paint. The cheap stuff is fine and here is the color code you will need to give them to get the right tint of green (note this is for a small 872ml or 29.5 fl.oz container) B-1 KX-11 AX-1Y31.5 D-1Y4
Advantages: Once a wall is painted there is no setup, smooth even surface
Disadvantages: Not portable, you have to have a wall to paint.
Last is to make a portable pop out chroma key much like a pop out reflector. Now these normally cost a fair amount of money to purchase but you can make one for really cheap by following the instructable I made a few months back. http://www.instructables.com/id/Pop-out-photography-reflector-or-chroma-key/
Advantages: Portable, less prone to wrinkles, looks pro, easy to hang or prop up
Disadvantages: Size limitations, sometimes wrinkles
Now this was short and sweet but really all you need to do is get yourself one or more of the options above and start experimenting. Have fun!