A paste is made by mixing powdered compunds containing metals.
A platinum wire is dipped into the paste and burnt at the blue flame of bunden burner.
http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/Elements_Organized_by_Block/1_s-Block_Elements/Group__1%3A_The_Alkali_Metals/2Reactions_of_the_Group_1_Elements/Flame_Testsristic colour can be observed for some elements are described in this article.