Writing a love song about tragedy and heartbreak that is set to a slow tempo, and putting fast heavy metal guitars, techno bass, and industrial drums behind it generally doesn't work too well. When writing, know what type of music you want as a background to accommodate the lyrics. For example, if you are writing a power ballad then know that most power ballads consist or rhythmic and repetitive backing instruments with strong guitar influence. This will help later on during recording, but also will help provide a basic idea of how you may want the words to go.
It may sound lame, but so will you if you constantly use the same words over and over. Changing words not only prevents overly repetitive lyrics, but also can help rhyming one line with another. Try replacing words like "love" with "infatuation" or hate with "loathing." Not only does this help to avoid repetition and help with rhyming, but using specific words to express feelings also makes a song more meaningful.
The typical song encompasses five distinct sections: intro, verses, chorus, breakdown, and outro. While it isn't mandatory to include all of these sections, or what order they should be in, it is good to know what sections you plan to use. Typically the verse is the main body of writing, and the chorus is the section that sticks with people. The chorus usually contains that one line that everybody remembers about a song. The breakdown is usually the section of a song right before a major change in the song. A typical love song consist of a traditional intro-verse-chorus-verse-chorus-outro, but this isn't a required structure. Write your song based on what sections you want to include in the song.
One of the most important aspects of writing a song is making sure it isn't the same as every other song you've written. Writing eight love songs about the same person, the same events, in the same sectional order, and the same tempo is not only bland but also annoying to your audience. Change your writing style from song to song.
The number one thing to remember when writing a love song is expressing yourself. More often than not, a love song is about your own experiences or desires. Don't try to write a song about your distant friend's long-distance relationship. Write what you know or observe keenly, and what you know better than anything else is how you feel--your own emotions. These songs are usually the most profound and captivating.