Your question is a recipe for disaster. A lawyer is normally the best place to start for contract work.
Alternative, a cheaper but not as secure way, is you writing to the client what you've agreed to do and what they are paying you for the work. Get them to insert that text on their letter headed Purchase Order and get it signed.
Most jobs like this are done with a signed statement of work/estimate which the clients signs- and then an invoice and off you go. If you really wanted to take the step of a format contract, try here: http://lmgtfy.com/?q=videographer+contract