THE SCIENTIFIC METHOD - The scientific method consists of stating a problem then; (1) make observations, (2) formulate a hypothesis, (3) design an experiment, collect and interpret the data, consult prior knowledge, and (4) reach conclusions.  

A good experiment has a large sample; it is controlled so that only one variable is assessed, it  is placebo controlled, and it is conducted in a double blind manner.  Scientific discovery is not always as well planned as the scientific method may seem to suggest.  Sometimes new knowledge comes simply from being in the right place at the right time or from being particularly aware of the unusual.  The opposite of the scientific method (and its organized planning) is discovery by "accident".

A hypothesis is a guess as to why something happens. Observations lead to questions regarding the event. Why is the sky blue? How does gravity affect falling objects? In attempting to answer a question about the nature of the world, a scientist will form a hypothesis (or a guess) regarding the question's answer.  Experiments, data gathering and study will then help the scientist to reach a conclusion.

References for "Thinking Like a Scientist"