I think I get too involved in my own writing that I’m blinded by the little mistakes, until I read it. By doing so out loud, the punctuations and subtle mistakes I’ve made becomes quite glaring.
Reading out loud also allows you a means to see if the words flow and carry a rhythm.
Sentences need to vary– Short sentences move the story though action, while longer, descriptive sentences are useful to slow the pace a bit.
Listen to the rhythm– Storytelling carries a certain music of its own. Read out loud a good book and it flows. This is what you need to emulate in your own writing. Syllables, tone, punctuation, all craft the ‘music’ of a story.
Edit as you go– I circle or highlight parts that don’t sound right. If I can’t fix the sentences, sometimes it means to get rid of it entirely.
This doesn’t mean I find every mistake, but the reading certainly helps in the editing process.