Step 1 - Main Idea.The title could be the first thing you do, or the last thing you do. But make sure that you think of your main idea. The main idea is usually something you feel strong about, something you want to persuade others, a story, an experience, etc. Just write down something that you want your song to be mostly about. You could now base the title off of your main idea or just wait and see if you want to use something else, but you are now ready for step 2.
Step 2 - Chorus.Your Chorus should be about your main idea, it shouldn't be very detailed tho. You should write about how you feel about your main topic; even though the chorus doesn't have to say your main idea, just write about how the main idea makes you feel or thoughts that you have. You don't even have to rhyme yet, just jot down your feelings, rhyming could come last if you wanted it to. Now onto step 3.
Step 3 - Verses.Your verses should support your main idea and/or your chorus. Now, the verses should be detailed. Still not having to rhyme, jot down reasons for the main idea, thoughts about the main idea, emotions that you feel while experiencing the main idea(you may have used these in the chorus, but you shouldn't have been detailing them, now is the time to go more in depth with your feelings about the main idea, etc. It's always best to use the five sense six if you see dead people) during the writing process, the audience will be more into the song this way. Do not make your versus too long or the song will most likely become boring. There is usually two to three verses in a song, but it is up to you.
Step 4 - Bridge.You don't need a bridge, a lot of music these days don't have bridges. Bridges are usually used when your main topic is something you feel. The bridge could be like what you do when the feeling comes over you. Usually a more aggressive part of the song.
Step 5 - Rhyming.Now that you have your chorus, your verses, and maybe your bridge, its time to make it rhyme. Go back to your brainstorming and start piecing it together, rearanging it, and tweeking it. If you can't make some of the words rhyme, find a thesaurus to find synonyms of the word you want to rhyme with, and start to piece that together (I suggest www.rhymezone.com for synonyms and rhymes, and many other ways to build your wording). You will also need a rhyme scheme, meaning how often the rhymes occur and in what order they occur. Having a good rhyme sheme is also very helpful when making the melody of the lyrics.
Step 6 - Melody.Melody always depends on what kind of song it is and what rhyme scheme you have. Sometimes it's easier to have a riff on a guitar or piano or something similar. I can't go in too deep on melodies because I have my own style and everyone has a different style (except pop music).
Step 7 - Structure.Time to put the pieces in place. The verse usually comes before the chorus and then theres another verse, and maybe a bridge, sometimes there's also a prechorus which is basically tying the verse and the chorus together, like a transition. but you can put your song together any which way you like.
