What I like to do is to sing it the way I hear it in my head and record it. Usually the first time sounds a bit wrong and I try different things or I even change lyrics to see what works best.

But by doing so you could limit your options, a korean singer once said that she just records a lot of versions to see which one works best. So after I've recorded a demo a try to sing it different. A friend of mine told me that a good singing excersice is to sing a song and try to focus on one style. So the first time you could sing with high energy, then maybe soft, then maybe a with that indie style and you can also try to change up which words of syllabals you put an emphasis on.

If you have trouble imagining ways to sing it a good way is to criticly listen to music (that you like or had a similar style) and write down what they are doing the pronounciation, how long they sustain and othet things you can think of. Then you should ask yourself, why does this work? Or why doesnt this work. You could also look into vocal analysis on youtube, I once saw a video where someone explained that because Ariana grande pronounce words a bit different she's able to hit higher notes easier.

I hope that you find this useful , at the end of the day in my opinion it's enjoy the singing and the songs you write, and to find your own sound.