There's nothing that'd remotely cut it as a one-size-fits-all guide to making a song.
Here's(a very general idea of) how I go about it though -
Imagine something(a rhythm, beat, and/or melody, etc.) and try to recreate it via software(like ableton) and/or an instrument you're comfortable with, and go from there. Sometimes I even remember music my subconscious came up with in a dream.
Improv on an instrument(or even your voice) until you find yourself liking a particular riff, pattern collection, general style or whatever, then you can record it or recreate it in software.
Tinker with the software directly, just start making and adjusting patterns and chords or even just some bars of a neat drum pattern if you like starting with timing over building it to fit with melodies. Experiment! I love just playing around for the sake of it.
Sometimes I'll use different variations of these approaches for different parts a single music piece. It's really just about whatever works for you personally.
After that I -
Pick my instruments. This can be more/less simple depending on the kind of music you're making, but I'm mostly a guitar/bass/drum + extra guitars and synth as needed kind of guy.
Listen to whatever I've started to make and get into the "soundscape" so to speak, and start getting ideas about where I want to take the greater composition. A good rhythm and beat will usually get me into making melodies in my head.
Fiddle with the different instruments, drum kits, sound effects and so on to get the right feel to each track. I might add an extra track to add very subtle background sounds. I may also try stuff like transposing to different scales, moving chord progressions, to adjust the mood. And so on and so on.
Then it's just a matter of polishing things up and getting down to the little details.
-Note that I'm not a professional, so take this with a grain of salt if you like.