The best writing, editing, and design are key to an effective resume. Next on the list is making the right choice about content. You have probably had a career that could fill many pages. Most of us have a tough time deciding to leave some things out. But you must. Your audience is impatient and has little time to spend on your resume. You want that time to be spent reading about your most impressive accomplishments.
If you were advising John McCain, you would urge him to omit his involvement with the Keating Five. Likewise, Senator Obama wants to avoid mentioning William Ayers. Both candidates are editing their resumes each day. Governor Palin, of course, has more serious challenges when it comes to identifying accomplishments.
A resume helps you organize yourself and see the full picture of your accomplishments and abilities. Most people take them for granted and may not have them uppermost in their mind at an interview. A resume crystallizes them. Go back through past jobs, highlight accomplishments that are relevant to the employer, and prune back those that aren't. For instance, while you would normally omit the person you reported to, include it if you know it will interest the company. Whatever you do, don't create a archeological resume, by simply layering new jobs and achievements atop the old ones. Be flexible.
Two specific goals to keep in mind when writing: 1) Focus on your benefits to the company, not yourself per se. See yourself from the company's perspective. Ask yourself what you'd look for if you were hiring. 2) Highlight your accomplishments, not your titles and duties.