The best way to ensure that you are using an appropriate statistical method is to consult a degreed statistician, preferably one who specializes in the field of interest.
In those cases where this is not feasible, then various other forms of guidance are available. A few are noted below. There may be (probably are?) others that are just as good that are not (yet) listed here.
"Intuitive Biostatistics": Choosing a statistical test
Statistical Advisor
StatSoft Statistica Help: Commonly Used Statistical Tests