Your resume is your first impression so don’t waste words, for example, describing all that clerical stuff you did in a past job if you have no intention of doing clerical work again. Even if you’ve mastered skills that are in great demand, don’t emphasize them if they’re not the skills you want to use in the future. Keep it simple and precise.
A resumé is a marketing document, not a historical record. Your current career goals should always determine which parts of your story to highlight and which to minimize.