First, the staffing industry specialist said that when she looks at a resume, she looks first for two things:

The resume must stand out. The specialist confided that she looks through a stack of 50 resumes in ten minutes. (Ten minutes!) That hurts, but, it is helpful to know the truth. Make sure your resume doesn't get passed over.

Since fields – their expectations, computer programs, laws, etc. – change, it is ok to focus on the last ten years or so, rather than digging much further back into your employment or skill history.

The resume shouldn't just be focused, but also customized for jobs.
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If you are thinking about applying for a few different kinds of jobs, you might craft separate resumes geared towards those industries.

A clearly stated objective helps to focus the reader's attention. Here are some tips from Monster.com about how to do that.

Keep your resume with you at all times. Talk about your job search with everyone you meet and network as much as possible. You never know who might know someone. Network with friends, former colleagues and contact any alumni associations you belong to.

The Smith College Career Development Office has some great downloadable worksheets to help you to put together your resume and portfolio: sample resumes, sample cover letters, interview questions, industry specific information, etc.

If you are listing computer or other skills in a section, make sure that those skills are still relevant.
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First, does the computer program still exist? Does an industry still follow the regulations you were once an expert in?

Staffing agencies or college career counseling offices can help you know your skill levels by giving you tests. Once you know your level (perhaps your typing speed and accuracy or proficiency level using a program such as Excel), you can decide if you need to improve those skills through tutorials or classes. Staffing agencies, college career counseling offices, public libraries, community centers and community colleges offer classes.  For example, the D.C. public library system offers "Job Seeker Drop-in Clinics". 

Staffing companies or college career counseling offices can help you with mock interviews, resumes, tests to see your level of proficiency with computer programs (or tutorials to help you improve) and more.

Before an interview, think about what you questions you might be asked. CNN has a clear and short article about how to answer some difficult interview questions.

Some general job search sites:

indeed.com (this site culls various human resources pages and newspapers for listings)