When I'm at work on a poem (a process of many days, even weeks), I often brainstorm ideas and words before bed. And hell if I want to get up every few minutes to look up some word or other association. So I have just gotten in the habit keeping my mammoth of a dictionary in bed with me. Webster is my best friend when I'm writing, and I often get caught up in the searching: one definition leads to another word needing clarification and another. When writing poetry I like to know the exact definition of the word(s) I intend to use, in each possible context, because often it is the implied associations of the word that are the most important, creating a web of meaning and a depth of story.