My method is one I find works well for me when I am starting a client's resume and maybe it will work for you if you choose to do your own resume. After I have all the information I need concerning where a client worked, what they did at each job and the dates they worked there, I start first by writing their Professional Experience in chronological order starting with the most recent. Then I go onto the Education, Computer Skills, Awards, etc. I find that once the body of the resume is complete it is much easier to write the Summary of Qualifications that goes at the top of the page.
If you follow this method you will find that all your jobs will be laid out in front of you and you can pick out what you feel are your greatest strengths to put in your Summary. If you try to start with the Summary before the rest of the resume is written you may end up flipping through pages of notes and hunting for the duties that you performed and essentially become overwhelmed.
Your Summary is so important as it is what a recruiter/hiring manager first looks at to see what areas of expertise you can bring to their company. Once they read your summary and like it they will go onto the rest of the resume.
Hope this helps and have a great day!