Always write about benefits to the employer
Your cover letter is a sales letter; you want the employer to "buy" what you have to offer. To encourage them to do this, it is essential that you explain how the employer will benefit if they offer you a position.
For example, if you have well developed interpersonal communication skills and you know these skills are important to the employer, then say you have these skills in your letter. Then go one step further and point out a benefit, for instance:
"I have highly developed interpersonal communication skills which means that I able to rapidly form effective working relationships with both co-workers and customers".
Avoid doing what inexperienced job candidates do which is usually to point out to an employer how a position with their organisation meets their career goals or other needs, such as:
"This is my ideal position", or "this role will give me the opportunity to get started/gain important experience in this field".
Employers will rarely be impressed by this; they much prefer to know about the contribution you can make, or the benefits you can bring to their organisation.