I was just researching a cocktail recipe and came across some really good advice from Robert Hess about stocking your bar. His suggestion is to start with your favorite cocktail, find the recipe and variants, buy all the ingredients and experiment with that. Then move on to the next and so forth. Pretty soon you will have the perfectly stocked bar and you will also have a pretty good mixing repertoire under your belt. Of course that is not what I did, but then I am Part of Head-case and therefore Hard-core.