Believe me, I was weeding out resumes (when working as a IT recruiter). Let me show you, fellow monks, how recruiter works. It is rather different from how you are looking for a position for yourself.

If you are looking for a job, you are tempted to apply for any position related to computers, hoping (and you might be right) you can learn mostly anything in 3 months.

If you are recruiter, you look at things differently. When you are looking for a candidate for a job, you start with one position to fill, job description, and thousands of resumes. You select couple of hundreds resumes mentioning certain keywords from job description. You need to weed out quickly as much resumes as you can, so you are looking for strongest skills first. If position ask for database admin, and you are strong network admin with some DBA skills, you will be weeded out - unless your cover letter says you are fed up with networks and fell in love in databases.

After weeding out, recruiter starts with 20-50 candidates to email/call. No more that 2-3 will be selected to be interviewed. Company does not want to be carpet-bombed by resumes - they are paying fee to select strong candidates only. If recruiter sends more than 2-3 candidates, s/he may lose business - and no candidates will be accepted. That is why focused cover letter (clearly stating position) helps a lot. And as a recruiter, I do not mind if a candidate sends me 2 weeks later another cover letter for another position, and resume is slightly different from previous one.
Also, as a recruiter you evaluate experience differently. Can you imagine that having too much experience is a red flag (if you have 10, when company ask for 3)? I'll tell you why: company suspects that you might accept job now, but might leave soon to more senior position. So if you have too much experience, you may want to state what other parts of job will be interesting to learn.

So when you are sending out resumes, your first goal should be not to send many resumes, but send maybe 10 with high chance to be considered "good fit" for the position. That is why cover letter is so important. First paragraph: what position you want to apply and where it was advertised. (So recruiter can link it to position - s/he may work on couple of positions simultaneously. Second paragraph: 3-4 most important skills for the job you already have (and are mentioned in resume), formulated using keywords from job description, or why position will be good fit for you. Chances are, recruiter will "weed in" your resume on basis on this cover letter only. Remember, IT recruiter most likely is not a computer person at all. S/he might know that SQL mean databases, but never heard about Postgress database or DBI. So do not bother mentioning deep technical details in your resume (unless jod description ask for it) - you will have plenty of time to mention it in your interview.

I tell you a little trick to fool programs scanning thousands of resumes for proper keywords. The higher "count" of keywords you have, the better score you've got. To increase your score (and also to improve resume readability for recruiters), add section "Experience" at top of your resume, mentioning just keywords, like:

Languages: Perl, C/C++, Fortran
Databases: SQL Server, Oracle, MS Access
Industry experience: Financial, banking, project management

If you are really greedy, you may want to add special section "Keywords:" (like if it is intended to computer scanning) and mention the same keywords again.

Obviously, to research a position for each letter to be able to use proper keywords in you cover letter, you need time.

I know many of you, fellow monks, want to believe that just email-bombing should do it, that you are increasing your chance to be considered. Do it, if you want (email is for free), but do not forget to research and send at least 5 focused letters every day. And network - about 50% of jobs are not published yet, or maybe person hired was fired after 2-3 months and position might be available again.

Remember also that company's goal is not to give you a chance, but to find a person able to deliver from day 1. So position should be clearly something you are capable to handle - or very eager to learn, with proven ability to learn quickly. You should build on your strong skills, and it should be obvious from your resume.

That is why many jobhunters recomment customize for particular position not only cover letters, but also resumes. I know it looks like lot of work - but we already agried that job hunting is full time job, right?

When you are applying to a position directly in company, it is helpfull to find a way how to bypass HR and contact directly manager. Look for a recommendation from inside. Why? HR weeds resumes out before contacting candidates. Manager needs to fill the position with minimum effort. Also, person recommending you might get a bonus for finding you, so s/he might be willing to describe you. But do not expect outright lying - his/her own credibility is more important than your job. But it was obvious anyway, right?

Many people do not like the idea that headhunters (recruiters) will get a fee for placing you. Do not worry about it - you are not paying it, company is paying. Make headhunters work for it: Call them about the position, ask questions to help you customize resume and increase your chance to fit. They might know something not published on web or in job ad. But do not try to fool them. Recruiter's goal is exactly like yours: You be hired and survive 3 months - because recruiter's fee is payable only after 3 months after succesfull placement.

Last advice: If somebody promises to find you job if you pay him upfront, it is not recruiter, but con-artist. Don't pay him.

pmas
To make errors is human. But to make million errors per second, you need a computer.