It's very easy to describe how to write songs, it's so easy that you will not find many text books on the subject. Anybody who has learnt to play an instrument (including here anybody who can sing)has the ability to write (or to make up) their own songs, the sticking point is usually the lyrics and that is why most sources of help concentrate on this aspect. But there are rules to help with most aspects of song writing to either get you going or help you over a sticky patch.
The best way to learn to write songs is to listen to the efforts of others and get a "feel" for it. The phrasing and structure should come with little effort. What makes a "good" song is the ability of the writer to "invent" something new and pleasing, using the elements of melody, rhythm, timing and harmony and of course lyrics.
Each element can be used individually or in context with one or more of the others to create that something special. Just listen to songs you like and try to analyse how the writers use these elements. It is here that the rules can help also, to help define what makes a certain song "catchy" or "different" or "memorable". To help repeat the, dare I say it, formula; and more importantly how to develop it to be your own!
Here I try to give some of the rules which novice song writers may find useful. I hope that you enjoy yourself with these and perhaps you may even produce a future hit.
HAPPY WRITING.........