Hubspot advises on how to write job vacancy posts that attract ideal candidates. 

Link: How to write a job description

This post advises on:- 

• Study your target candidate 
• Optimize the job title with keywords
• Start with a company summary 
• Concisely describe the job's benefits
• Summarise the benefits package
• Keep the job's requirements clear and realistic 
• Use strong verbs to describe the job's responsibilities 
• Remove bias from your ad