How to make a song is such a tricky questions because it is a very subjective topic, I mean I can share some of the ways that I compose and may be it can work out with you.
So I start with the melody most of the time , I mean I create melodies while Playing guitar, bass , piano or Synth and then I put some cool sounds around it obviously in the same key , kinda making it more of a balanced harmonic collaboration of sounds , I mean each sound elements mean a lot to me when it comes to composing , because each sound element has a certain vibe and in order to make a nice song all these elements should vibe in , vibing in is really important for eg if the frequencies in your Melodies and chorus are not in synch then you can’t do justice to your song because they aint vibing in , trust me it should sound pleasing to you and if doesn’t feel good then you aint doing it right..
After I am done with the melody I add the drums and percussions , I make sure that I don’t overplay , I just use a nice minimal structure when it comes to my songs , my focus is to always integrate the melody , harmonics and rhythm in the most subtle and smooth way , I keep it simple and minimal because in the end you will see that the song build up so many melodic elements that even you are taking a minimal approach it may sound real wide and muddy. So once I am done with the drums , or let’s say the rhythm which for me is the bass and the drums , then I move to vocals.
I am more of a feel oriented when it comes to vocals, based on the music I add vocals , and this is what I do all the time , the process can be totally opposite for lot of musician but for me music comes first before the vocals , it is just easy and free flowing for me when I have a good lead and rhythm going on , it helps me to get in to the vibe , obviously all songs have a different kinda vibes and may be your way of producing a track will be different then my , you can have whatever process that works for you until and unless it is effective and efficient.
Make it an easy process, making a song is not a rocket science, i know if your are new to the game it may feel like what the heck is this, but gradually you will see it will come automatically without much effort.