A few weeks ago I got this really great book by Judika Illes titled Encyclopeadia of 5000 spells. It is a great reference book and a fun read. This made me think about the reference books I typically use when ever spell crafting. One of my all time favorites is Tarot Spells by Janina Renee. This book literally changed the way I do spell work. I find that tarot cards are a great way to draw in universal energies and archtypes and help focus the mind for visualization. Also I don't think I've worked a spell in the past 10 years when I didn't reference Scott Cunningham's Encyclopeadia of Magical Herbs..
All that said, I never do spells straight out of someone elses book even when the book is fun and well researched. It is my experience that magical use items (things like oils, candles, color symbolism, incense, tarot cards, herbs, flowers, etc.) are like magical yeast. You use yeast to make bread rise and to create a transformation. Each recipe is unique and your bread won't be *exactly* like anyone else's. How you use the magical yeast depends on what you are trying to make and the conditions surrounding the issue. As any baker can tell you, the environmental conditions might mean that you have to alter the recipe. This is why all magic should be carefully evaluated in context and carefully "crafted", before acting.
They don't call it witchCRAFT for nothin'. This is also why the saying "Be careful what you ask for" is something even "muggles" understand.