5 Steps To A Successful Song:
Write the song in the form of a story. This kind of song is interesting to listen to and will keep listeners hanging on till the end of the song.
Revise the song as you go along. If you don't like how it's turning out, don't scrap it, just start over. (You might want to get ideas from that song, maybe it can help you get through a writer's block).
Use simple words. The song should contain mostly simple language. No matter how complicated your feelings are, too many complicated words may overwhelm the listener.
Use short, well chosen words. A thesaurus or dictionary can be helpful here. (It's also a good idea to check with friends that the meaning you're trying to convey makes sense to them too.)
Make sure the song's rhythm flows, otherwise it's beat won't catch on and it will be hard to remember. Think catchy and original.
Of course, there are always exceptions to the "simplicity" principle. If you're an amazing wordsmith who can get complicated language across in a way that draws in an audience, go for it. The curiosity factor and rumor mill can do wonders for the success of a song.
Focus on the chorus. What is the main message you're trying to convey? Is it catchy and manageable for people to start singing for themselves? If it's convoluted, strange or hard to hear, listeners will hum or sing "oooouuuuww" instead, so take care here.
Don't be too blatant about your meaning in the song. Use metaphors, don't just flat out say your point. You might even start out just writing words that sound good together, and let the meaning emerge later. When you start writing a song, you don't always have to know how it will end up.
Try writing a chorus first so you can base your ideas off it. This also allows it to take up most of your song but don't make it too long.
Write from your heart. This means that you pour a piece of yourself into the song, your passion and your commitment to the song's message. A song written from the heart will enable those who listen to it to completely get into the song, wanting to hear it over and over again.
Get an audience. Once the song is complete, let other people hear it and ask them what they think. This should tell you if you did a good job or not.
Also ask your listeners to interpret the meaning of the song. Many people won't get it at first (at least they shouldn't) but eventually they should figure it out.