In addition to the basics, there are a few more things you can do to make your cover letter-writing experience more effective and less miserable.

1. Be The Boss
If you get stuck on what to write, pretend you are the boss of the company.  Write what you’d want your dream employee to be like (so long as it all still pertains to you).  This helps you display that you’ve got what the real boss is looking for.

2. Genki Desu!
You know how in every anime, there’s always a hyper character who is ridiculously eager to please?  When they want to be class president or what-have-you, they don’t just list their credentials.  They go CRAZY listing everything and showing how it makes them the perfect candidate.  If you’re staring at a blank screen and a blinking cursor, try pretending you are a hyper anime character and write a madly long list of every crazy reason you can do the job.  Then, take a short break, and come back to edit it down.  It’s easier to delete the stupid things afterwards than to write while censoring yourself.

3. Write a Poem
Don’t worry, the poem doesn’t get submitted anywhere.  Just try explaining why you’re the perfect candidate for the job – in rhyme.  True, not all poems have to rhyme, but this one does.  The reason that rhyming helps is because it’s harder, so it makes you think of alternate ways of describing yourself.  Also, if you’re trying to fit a rhyme scheme, it may force you to rearrange your rote speech.  This means you will come up with ideas and combinations thereof that aren’t so obvious.  Therefore, when you rewrite your poem as a normal cover letter, you’re incorporating ideas that perhaps other applicants aren’t.

4. Proofread in a Funny Accent
No, this is not just for your own amusement (although, it helps).  If you can’t get someone to proofread for you, I suggest taking a five-minute break looking at something else, and then proofreading your cover letter in a funny voice.  Pick a cartoon voice or accent that you’re NOT good at imitating, and read out loud.  This is effective because it forces you to focus on every single syllable, and therefore, it helps you catch typos.  Just, um, do this one at home and not out in public somewhere.