There really isn't a standard way to write a song. Everyone approaches it very differently, so it's hard to nail down the most appropriate method. That said, there are a couple of techniques that you can use as you begin to learn.
Words first:
As it says, with this method you write the words first before you right a melody and a chord progression (or harmony). Many people like this technique because you can literally write half of the song out before even touching an instrument. For technique, this method is particularly effective.
Music first:
I remember this as the method that uncle Jesse and uncle Joey used on "Full House". Basically, you start at the "bottom" with a rhythm; then move on to a chord progression; then to a melody and harmony, then you write words. This can be very effective if you have a musical background already. A benefit of this method is you can use common chord progressions to create the body of the song and then fill it with the melody and words. However, the biggest issue is that your songs will tend to start all sounding the same (like 4 chord songs).
A good first step regardless of which technique you use is to name the song. It may sound like putting the cart before the horse, but think about it this way: You are writing the song to convey an emotion or tell a story, right? Well, wouldn't a simple two or three word name help you stay on track to the song being written?
~DB