1) Read it out loud to yourself. Have you missed words? Do you trip over anything? 2) Read it aloud to two or three people who are unfamiliar with your industry. You're looking or understanding and reaction. Ideally, you'll hear _ hey, do you do that? That's how you tell you've gone beyond examples of good cover letters and they're enthusiastic.
The third and last paragraph provides means to follow up your application. You can slightly review what you have previously mentioned in the letter to provide more emphasis. You can also provide means for contacting you in case you are considered in the next phase of the application process.