List your qualifications in order of relevance: Begin with the most relevant to the least. Only list your degree and educational qualifications first if they are truly relevant to the job for which you are applying.
Quantify your experience wherever possible. Cite numerical figures, such as monetary budgets/funds saved, time periods/efficiency improved, lines of code written/debugged, numbers of machines administered/fixed, etc. which demonstrate progress or accomplishments due directly to your work.
Begin sentences with action verbs. Portray yourself as someone who is active, uses their brain, and gets things done. Use the present tense for your current position. Use the past tense for descriptions of previous positions.
Don't sell yourself short. This is by far the biggest mistake of all resumes, technical and otherwise. Your experiences are worthy for review by hiring managers. Treat your resume as an advertisement for you. Be sure to thoroughly "sell" yourself by highlighting all of your strengths. If you've got a valuable asset which doesn't seem to fit into any existing components of your resume, list it anyway as its own resume segment.
Be concise. As a rule of thumb, resumes reflecting five years or less experience should fit on one page. More extensive experience can justify usage of a second page. Consider three pages (about 15 years or more experience) an absolute limit. Avoid lengthy descriptions of whole projects of which you were only a part. Consolidate action verbs where one task or responsibility encompasses other tasks and duties. Minimize usage of articles (the, an, a) and never use "I" or other pronouns to identify yourself.
Omit needless items. Leave all these things off your resume: social security number, marital status, health, citizenship, age, scholarships, irrelevant awards, irrelevant associations and memberships, irrelevant publications, irrelevant recreational activities, a second mailing address ("permanent address" is confusing and never used), references, reference of references ("available upon request"), travel history, previous pay rates, previous supervisor names, reasons for leaving previous jobs, and components of your name which you really never use (i.e. middle names).
Have a trusted friend review your resume. Be sure to pick someone who is attentive to details, can effectively critique your writing, and will give an honest and objective opinion. Seriously consider their advice. Get a third and fourth opinion if you can.
Proofread, proofread, proofread. Be sure to catch all spelling errors, grammatical weaknesses, unusual punctuation, and inconsistent capitalizations. Proofread it numerous times over at least two days to allow a fresh eye to catch any hidden mistakes.
Laser print the resume. Use plain white paper for copies, and if sending via email, save the resume in PDF format so the formatting is retained. For copies you intend to take to the interview go to the office supply store and find an interesting high-quality paper. You want your resume to say quality at every level, even down to the paper you print it on.