Writing a song on an instrument can be a tough task especially if you dont have guidance. I know this because I too found it pretty hard until my teacher gave me some simple steps to start with and that for me was the way.
Here are the steps:
1) Decide whether you want to write in the major scale or the minor scale. If you dont know about them yet, learn them first. Scales refer to a series of notes that go in an ascending and descending manner. The
major scale is the foundation from which all other scales are formed. A C major scale begins with a C and ends with a C. The same rule applies with the rest of the keys where a D Major Scale begins and ends with a D and so on. The notes on a major scale is numbered from 1 to 8, this signifies the intervals.
the major scale looks like this:
If there are major sclaes there are also minor scales. The notes on a major scale sound bright and cheerful while notes on the minor scale sound solemn and sad. There are three types of minor scales and I think this would get us off topic so here is the natural minor scale.
2) Once youve done that choose a key. A key can either be in major scale or minor scale for example major scale in the key of C would have the notes C D E F G A B C. If you choose D then D = D - E - F# - G - A - B - C# - D. Lets say you wanted to write in C major.
3) Now, each note in the C major scale refers to a chord. So the chords you could use are C D E F and G. These chords would always sound good together as they are in the same key and this answers the question of many new guitar players of how to find chords that sound good together, well this is the answer. You could do this with any other key for example B minor. Remember, the notes in the scale correspond to the chords you could use to stay in that key.
4)Now, you take any 2 or 3 chords out of the ones you've found in step 3 and play them together. Try different techniques and strum patterns. Also try different tempos and variations. You could use open chords, barre chords, diminised chords or power chords, whatever you like, it depends upon the genre you want to write in. You could use the palm mute technique for punk rock style or power chords with distortion for heavy metal or open chords on electric for classic rock .
5) Now, that we have some music lets break that too. First the intro, then the verse and then chorus. Use different chords or same chords with different strum patterns and tempos but if you use different chords make sure they are in the same key.
6) Put a melody over it and start writing lyrics.
I hoped this article helped you, you can expect more from me very soon.