Decide what the purpose of your song title will be: if it will serve as a general summation of the song, an eye-catcher for other artists who may want to purchase the song from you, or a reflection of the overall feel of the song itself.
Brainstorm words, phrases and even stream-of-consciousness thoughts. List them on a piece of paper regardless of whether you really like all of them or not.
Narrow your list by focusing on specific words and phrases that stand out to you and best align with your vision of how you want your song to be viewed or understood. You can either strike out ones that don't make the cut or highlight the words/phrases that do.
Re-read the lyrics of your song, keeping every potential title in your mind while doing so. Think about how well each possible title fits within the context of the song's words, and perform this step again while listening to the song's music track for a fuller effect.
Refine the song title you have determined fits your song the best. This may involve adding or subtracting a word, or changing the word order a bit for the most natural flow.