Dear (insert last name of contact if you have it, or the position, such as ‘Hiring Manager’),
Paragraph 1: Indicate which post you are applying for and why you think you would be suitable for the post. You can use some of your experience and qualifications to back this statement up, but just touch on these.
Paragraph 2: Go into more depth about your previous experience and qualifications, mentioning specific roles and qualifications that are particularly well matched to the position advertised.
Paragraph 3: This should be a concluding paragraph where you thank your reader for their consideration and mention how keen you would be to be considered for interview.