Determine what, exactly, you want to find out. This will guide the development of your hypothesis.
Make a prediction as to the outcome of the experiment or study. This is the hypothesis. For example, in an imaginary study of a new cancer drug, you may hypothesize that X drug will reduce mortality in cancer patients.
Establish an independent variable. This is the presumed cause that will be tested for. In the given example, the patients administered the experimental drug X will constitute the independent variable group.
Determine the dependent variable. The dependent variable is the factor that the independent variable acts on. In this case, the dependent variable would be cancer mortality rates.