Here are some good starting points for writing a great song:

The song must evoke or provoke a feeling within the listener, something they feel speaks to them. Often the listeners interpretation of a song has nothing to do with what the composers original idea was but that isn't really important, the fact the song is able to mean something different to each listener is all that matters. Remember, if you aren't feeling the song the listener probably won't either.

Don't beat a dead horse! If you have to consistently work on a song over and over and over again chances are its not going to be the masterpiece you think it is. Ask any good songwriter and they'll tell you their best song practically wrote itself. If you re having trouble with a song, step away from it for while, come back to it later, and see if any new ideas come to you.

If the song has lyrics the listener should be able to be easily understand them without too much thought provoking. Simple and straightforward is often the best way to get your point across.

The song must have something truly memorable about it. Often this is the melody line although it could end up being a solo, certain sound, or even a rhythm. A catchy melody or riff that the listener can walk away humming will almost certainly make them remember your music for quite some time. Most "hits" have a memorable melody line.

The production of the song must be done well enough to hold the listeners interest for the entire song. Too little production means the listener will get bored too quickly, over production can cause the listener to tune out even faster. Knowing that fine line between the right production and over produced is a difficult one to learn and a common mistake amongst most songwriters who try to produce their own music.

Keep the song short and sweet. While 15 minute tunes from the likes of Yes, ELP, and Genesis may have done OK in the 60's and 70's that doesn't fly today. Its pretty difficult to get your point across if nobody is able to hear your music. No radio station today will play a song that exceeds 5+ minutes so take that into consideration of you want the masses to hear your music.

Make sure your arrangement is interesting. Like it or not there is a classic formula for making a song and the intro-verse-chorus-verse-chorus-bridge-verse-chorus-chorus-out formula still holds true. Sticking to this formula isn't a must but it can help in making a better song.

If your song has vocals the delivery of those vocals is extremely important. Singing with heart felt emotion is a must and if you intend to sing your own song be certain you have the vocal ability to get your idea across. If you don't have great pipes, consider hiring a vocalist who can do your song justice. Nobody likes to hear seriously out of tune vocals no matter how great the song may be.

If you can write a good song but lack the musical ability to play and record it well, hire someone who can do that for you. Knowing how to put the song down in a manner which is appealing is important. If that means hiring musicians, a producer, or an engineer by all means do it. If you believe in your music strongly enough then spending a few dollars so that you can have a well done project that you can show others is quite beneficial.

Be your own worst critic. Remember, if your song isn't of the same caliber as what you hear available commercially chances are you need to keep working on it to make it better. Being able to be honest with yourself as to whether or not your song has what it takes to make it in the real world is a difficult thing to do. Not every song you write will be good, many will be stinkers, and if you are lucky enough some may become the standards of tomorrow.

Writing the song is one thing but bringing all the elements together to make the song a finished product is another. Once the song has been written and recorded now comes the hard part, marketing it so that you can allow others to hear your works. Radio airplay is hard to get and even harder to keep. If your song is catchy, has something unique about it, and can hold the listeners ear, chances are you'll have a hit on your hands and a song that may be around for may years to come.