The scientific method is utilized by
scientist as well as others to critically evaluate and assess the
natural world. The scientific method can provide you with a guideline
on how to conduct, evaluate and follow up scientific experimentation.
The many steps of the scientific method are depicted in this overview:

References on the Scientific Method
and Scientific Thinking:
The Free Encyclopedia-- extensive explanation:
http://www.wikipedia.org/wiki/Scientific_method
This is science--includes alternates
to the linear scientific method, including multiple working hypotheses
http://www.ucmp.berkeley.edu/people/jlipps/science.html
John Platt 1962 paper on Strong Inference,
nice discussion of T. C. Chamberlin's multiple working hypotheses
http://www.cof.orst.edu/cof/fs/gradprog/courses/radosevich/science.htm
Biology Project tutorial using the scientific method
to investigate breast cancer
http://www.biology.arizona.edu/cell_bio/tutorials/cells/cells1.html
Teaching Critical Scientific Thinking
http://www.carleton.ca/~tpatters/teaching/climatechange/sciencemethod.html
http://teacher.nsrl.rochester.edu/phy_labs/AppendixE/AppendixE.html