Writing lyrics to a song is one of the hardest parts of being a professional music artist. There are so many factors to think about and writing a hit is even harder.
The way that I write my songs is I listen to one of my favourite artists (Rise Against, City and Colour, Enter Shikari, Nighttime in Kansas and a few others) to help me get the creative aspect going. I personally like to have my music tell a story about an event in my life or an article I've read. For example, my song "Two Wrongs" is about an article I read. The article was about a woman whose son is on death row and how weird it is to know your child will eventually be killed for what you consider a simple mistake he made as a young adult. I just find that I personally can get inspiration from anything. Many artists use similar methods to the one I use or just write about things that they experience in their daily lives. "Money For Nothing" by Dire Straits was written inside a department store while Mark Knopfler listened to a worker rant and rave about musicians getting paid for almost no work. "Wonderful Tonight" by Eric Clapton was written while he and Paul McCartney waited for his wife to get ready for a party.
Once you find your inspiration you now should just write what comes to you. Even if it doesn't make any sense. You don't even need to write it in the format of a song. I also find that writing the first draft on paper makes a huge difference to my writing style. I always write on paper first. After you write your first draft, open up your computer and start typing what you wrote on paper up on your computer. Feel free to make changes as you type. As you're typing, you should change it to a proper song format.
There are many different styles of song writing. The most popular format is ABAB or verse chorus verse. A variant on that is ABCABC or verse pre-chorus chorus verse. Your verse should tell the story and move it along for example here is the first verse from my song "Two Wrongs":
I know that you lost your babyBoy that dayBut I think that you should knowThat I did tooEven though we both experienced such aMassive loss, yours seems so much worseTo everyone except me.
The chorus should build upon the story but not move it along too much. Here is the chorus to "Two Wrongs":
I just want you to understand thatEven though my little manMay have stolen yours away from youTwo wrongs don’t ever make a rightPlease, please don’t let them take himOut of this world.
Your chorus should be similar every time you come around to it but it doesn't have to be a carbon copy. It should have the title to your song in it but it doesn't have to. A pre-chorus should build off of the verse and lead into the chorus. I personally don't write pre-choruses but they do have their merits!
A very useful tool for all song writers is the refrain. The refrain is a line that gets repeated throughout the song. For "Two Wrongs" it is the line: "Two wrongs don't ever make a right." Other useful tools for songwriters are the thesaurus and a rhyming dictionary. The number one thing I always do is write and re-write until I'm satisfied. I also ask bandmates and friends for advice on lines. Don't always worry that people will demand a cut of your royalties because most people don't even care, they just want to help you out!