By making a song mine, I don't mean coming up with my own unique interpretation of a song that nobody else ever has done before. No, I mean more that I own the song, that it is in the metaphoric portmanteau I carry with me through life.
So I should start by saying that for me, leading songs is not about performing in its usual sense. The goal is for as many of the people present as possible to enjoy themselves, to join in as much as they can, to be part of the sort of collective joy that chorus songs bring. The goal is for people to think "What a fun song to sing", not "Steven sang that well" -- so this is what comes into play when I work on presentation. I do not have a "pretty" voice, I don't even have a completely reliable sense of intonation or a quick ear for melody. But what I do have is a strong voice and rhythmic drive, and an absolutely sincere desire to connect with the people present when I sing and to help them connect with each other. This is what I work on, and this is what I think I bring to a room.
So that means that first of all I feel I must be absolutely spot on my sense of pitch, so that I can give the room what it needs to hang onto, either to learn the song cleanly if they don't know it or to find the overtones to harmonize. There are people who are quite gifted, for whom this is not something they ever have to think about. I am not one of those people. I will play a song over and over and over, then walk away from it and work on it, then return to the music or the recording and see where I have strayed (the gifted folks I speak of simply do not stray even on one or two hearings). If there's an interval that causes me trouble I sing that interval over and over until it's in the muscle memory of my voice box. Still I mess up more than I'd like, but I give it my best.
And then, of course, there's the words -- knowing the words so well that each chorus leads right into the words, and they are simply there to hang the notes onto. Again, I will sometimes mess up here as well, but pauses while people try to remember words (understandable and inevitable) do detract a little bit from what I'd like to help create by leading a song.
But it's not just avoiding the pauses of forgetting a verse -- actually verse-forgetting is part of the charm of live community singing. I want to know what the words are doing -- how they are telling a story, or how their rhymes and sounds interplay. I want to find the subtext, even if that subtext is only "shout for joy because this is a silly rhyme". Simply knowing the words is not enough, not until I've sung through the words many times in my head, exploring their story. I can then make eye contact with the people present, telling them the story directly. I have to own the words to do this.
And then there's trying to understand how the musical flow works with the words -- where the melody swells with the meaning of the words, where the melody bends the natural accent of the words and where the accent of the words alters the rhythm. That is something that I find just gets richer with repetition -- it's why I'm not bored singing for a Molly dance even on to the 200th time. There is always a spontaneous, live interplay of words, story, rhythm, and melody. But this is all on top of knowing the words and the tune. These are the ways I make the song mine.
Sometimes there's also the matter of keying the song, not just where I can simply hit all the notes but where the notes feel right for my voice for this song. In the song I've been learning for tonight, the verses sit at the top range of the song -- the first note is the second-highest note in the song -- and then the refrain pulls things down. So I can't just open my mouth and start singing where the verse feels comfortable and easy or the later line "and oh what a lonely song he sings" doesn't ring out mournfully where it should; the slightly-held "oh" is the very top note of the melody and it feels wonderful when it falls towards the top of my vocal range.
For me to feel a song is mine and thus to sing it, I need to be able to grab the song from the air, to convey something to the people singing it with me, to make it easy for them to feel it and sing it as well. I need to know in my head where the song is and where it's going and where it will end up, throughout the song. I am simply not talented enough to do this without advance work.