A good job description lets potential employees know exactly what the job entails so that they know what they're getting in to. While it's impossible to include everything, incorporating certain pieces of information means you'll get the candidates that you need.
A good job description should state the job title at the beginning, with the salary expectations. A lot of people ignore jobs that advertise "competitive" salaries as that's often a euphemism for "low." In addition, it means that people know what you're potentially offering before they even apply, and those who want much higher salaries than you can offer are put off.
Naturally, a job description should include a description of the job. Traditionally, the description should detail who the applicant will be reporting to, a short summary of the job expectations, major key performance indicators that the applicant will be expected to adhere to and a brief list of qualifications.
The qualifications should be as specific as possible to ensure that your applicants know exactly what they need. Clearly separate necessary requirements from desirable requirements as, particularly in small industries, not all applicants will have every desirable requirement. Make sure that the person your applicant will be reporting to gives input in all of this.
In competitive industries, the job benefits are important, although vacation time, sick leave, pension schemes, discounts and subsidized catering are fairly standard. Highlight anything that's unusual or unique, however, particularly if you're in a tech-heavy area. All of this should be under 500 words, so try to keep it reasonably brief.
Perhaps the most important piece of information in a job description is to clarify exactly how you want applicants to respond, but include that at the bottom. In addition, if you request that applicants contact you by email, set out exactly how they should format the subject line. This ensures that you can immediately discard anyone who hasn't read the instructions properly, saving you a lot of time.
When sorting through the job applications, a number of companies use keyword software, but that's not always ideal, as not everyone includes exactly the same information in the same sort of way. Look through potentially qualifying applications yourself to build up an idea of the sort of applicant who is applying. If you're getting a lot of irrelevant applications, consider modifying your job description to eliminate typical irrelevant applicants. In addition, you might consider raising the salary if you're only attracting underqualified applicants.
Ultimately, a good job description is a piece of advertising that catches your ideal applicant's eye. It needs to include all the job benefits, from salary to working conditions, and a comprehensive list of various requirements. It should be unique for each position, be approved by the potential line manager and detail exactly what the applicant needs to know.
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