I think the rule of thumb is to first stock those things that you prefer to drink. So for me that would be Ketel One, Bombay Sapphire, El Dorado 15, Lagavulin 16, Clyde May's Alabama Whiskey, an anejo tequila, Sambucca Black and Lillet Blanc for my Vesper Martinis. This also assumes I've got some differents on hand as well as some nice red wines that I like. The thing about my needs is that I drink everything straight. No mixing. I drink each one on the rocks. Obviously the Vesper involves mixing them. But then I'd probably want some other spirits that are more suitable to mixing. And that portion of the collection would likely reflect who I have visiting enough to warrant having stuff on hand for them. I wouldn't go by the "bartender's guide" because it would likely cost a small fortune to have everything they suggest. It's kind of like what they tell you on an airplane. In the event of an emergency, put your own mask on before attending to your children. It applies here too.