What should you have on a contract?

[Rockn]

I been working in the bussiness a little while. fairly new. I decided that I should do it by contract seeing as how people always want to add stuff which is money out of my pocket. So I was think maybe going with a contract so this way if they want to change something. they'll have sign a contract and pay a little extra for anything extra they add in the job. Can someone help me out please on what should be on it or a sample one?

[bohiaa]

Everyrthing should be on it. out line all of the what if's

[AI Inc]

And always keep blank change orders with you, have them sign it before any additional work is done.