When responding to a job advertisement, your cover letter is as essential as your CV, and forms part of a package. It should generally be typed on good quality paper, either white or possibly cream. The only slight exception might be if you are applying to a creative industry, but even there it can be better to be cautious.
Make it clear which job the application is for – this may seem obvious, but if the employer is filling several jobs you may get lost. The letter also needs to draw attention to how well you fit the job requirements. The best way to do this is often the T bar letter.
After the first paragraph, lay out the next paragraph in two columns. The first sets out the requirement, the second how you meet it. This makes it easy for the reviewer to see the match. Pick the 3 or 4 most important requirements – if you get as far as No 17, you are overdoing it.
Close with a standard paragraph, and keep to one side of A4 as a general rule.