A service that I perform for many of my clients is helping them to improve their resumés. It surprises me how many people still view their resume strictly as a summary of the positions and responsibilities they've had, headed by an objective statement that delineates what kind of job they're looking for, and perhaps the kind of organization as well.
Yes, a resume does have to accurately reflect your work history, but it needs to do much more: it needs to make a strong enough sale of your qualifications to get you an interview. It's the interview that will determine who gets hired and who doesn't, not the resumé, which is merely the door opener (but, of course, essential). What the resumé should not do is use up space specifying what it is that you are looking for. Remember, if you're submitting a resumé you're obviously looking to be hired for that job or, in more general cases, by that organization - no further elaboration necessary.
Nowadays you can be sure that there will be many qualified applicants for any given position, so a good resumé has to persuade the reader that you will be able to make a significant contribution to the organization. That means that your resumé should be specifically tailored to the position being applied for. Yes, it's extra work to alter the resumé for every application, but a "one-size-fits-all" resumé often misses the opportunity to specifically highlight accomplishments that are most relevant to the organization seeking to hire.
Some very specific suggestions:
1) Readability - Remember that whoever is screening resumés for the position is probably reviewing many dozens of (if not hundreds) of resumés, and fatigue / monotony is a very real factor in the process, so your resumé shouldn't appear difficult (i.e. dense). Make sure that your resumé has adequate white space, and that the font size is at least 10 point. Unless you're applying for a highly creative job, stick with a relatively "sober" type face (Ariel or Times New Roman, for example). Lines separating sections of the resumé can enhance visibility, and bullet points are easier to read than run-on text. No photos! Also, remember that the vast majority of resumés are submitted via e-mail. Make sure that the format remains intact when your resumé is forwarded.
2) Clarity - Too many resumés assume knowledge on the part of the reader that is possibly not there. Unless you have worked for a well known entity (e.g. General Electric, AARP, The State Department) be sure to spell out briefly what your organization does. When you get to your accomplishments / responsibilities, make sure they are articulated in a way that would be comprehensible to a relatively smart high school student (exceptions are academic and government resumés). Use numbers whenever possible (e.g. "Revamped newsletter, increasing readership by 56%;" ""Exceeded sales goal by 20%;" "Supervised staff of 13"), but better no number than a number that is insignificant (e.g. "Average profit growth per annum of 4%) or clearly an attempt to quantify something that is not quantifiable (e.g. "Enhanced company's reputation by 50%).
3) Length - A one page resumé is by no means essential (although it may be a good idea to try to boil yours down to a page, forcing you to focus only on the most salient and impressive points). In no instance should you go over two pages (again, with the exception of academia and government).
4) "Summary of Qualifications" should generally begin your resumé (I often refer to it as the "headline" of the resumé; I think it's often helpful to think of your resumé as an ad, designed to sell you as the product). "Professional experience," " Professional Profile," and "Work Experience" are titles that I frequently encounter at the top of a resumé; but I think they are somewhat less effective than "Summary of Qualifications" because the latter has more of the feel of "here's why I'd be a great fit for this position." There are experts in the field who feel that the "Summary" is at best superfluous and at worst annoying, and I agree that this is true if the qualifications cited are overly broad or vague. But a "Summary of Qualifications" that is specifically addressed to what the employer is looking for helps the applicant structure the resumé in the most logical and persuasive way.
5) Education - If you've been in the workplace for more than a few years your educational information should be placed below your employment information, unless you excelled at a particularly prestigious institution ("Magna cum laude at M.I.T." is pretty impressive!). Year of graduation can be omitted if it too clearly indicates an age significantly higher than you'd like. High school honors and activities should definitely not be included unless you are just out of school.
A word about cover letters. They're not as important as most people think. However a good, "punchy" cover letter that clearly articulates your qualifications (along the lines of the Qualifications Summary) is a nice adjunct. Don't waste the reader's time with "This is to apply for the position of assistant vice president...."; use a more forceful statement, e.g.: "The attached resumé demonstrates the ways in which I would make a significant contribution to......" followed by a crisp list of bullet-pointed assets. And don't forget to ask for the interview!