How do you find order of reaction from chemistry data?

Thats a very complicated question in very few words.  I'll do my best to give you a short answer, but its very easy to get invoved with gasses, and that will completely give you different equations.  Just remember that: The rate of reaction is proportional to the concentration of A or
The rate of reaction is proportional to the square of the concentration of A

If a gas was given off during the reaction: A+B > Products