2. Consider What the Song Does
It bears stating that not every Christian song out there is or should be considered a worship song.
Songs for worship generally fall into one of two categories: either they fill a role in the service or they teach us something about God. Other Christian songs may be about life experiences or even elements of our Christian walk or struggles, but they aren’t worship songs. (Side note: there are certainly times to use non-worship songs during worship, such as to illustrate a point or setup a message. But as a song to be added to the rotation of songs for the congregation to sing, they don’t qualify)
Songs that fill a role in the service act as a part of the liturgy. The liturgy is simply the pattern of worship, but traditional liturgies contain important things like the Invocation, Confession of Sins and Confession of Faith among other things. In our “Non-liturgical” style of worship, we still incorporate elements of the liturgy in our service – just in the form of a song and not responsive readings.
Songs that teach us about God need to be grounded in scripture. Because of the way worship songs tend to be written, you may find that there are several ideas present in a song, with just a line or two about each idea.
» For more about choosing good lyrics, check out this post from a few years back.