There are many methods of determining what is what inside of a mixture.  Some of the more simple methods are finding the melting or boiling point of a substance to determine what it is. 
     A more complex method is flame ionization.  A flame ionization detector absorbs burned substances and detects the concentration of each product of the combustion, yielding an empirical formula.
     Infrared spectroscopy is a machine that can determine the identity of organic functional groups. 
       Nuclear magnetic resonance spectroscopy will help you determne the chemical structure of a substance by giving you a series of peaks to look at and decide the identity of it.  This is an example of what data you get from a NMR spectroscopy.


     Mass spectroscopy will tell you the molecular weight of a certain substance, then you can look up substances with that molecular weight and similar properties to your substance.  The all in one for identification methods is the LCMS, which is    
     Liquid Chromatography Mass Spectrometer.  This machine will separate mixtures and then help you identify them.