You now have your first draft. It's time to take your script and make sure everything reads out loud the way it sounds in your head.
Pay attention to anything that feels clunky, that you have trouble saying, or otherwise doesn't feel quite right. Make the necessary corrections. Often times, things that look good on paper do not translate well when spoken aloud. Before you really start to polish your wedding ceremony script, read it aloud to catch phrases that may trip you up or otherwise feel cumbersome when recited aloud.
Find someone to listen to you rehearse the ceremony. Having a second pair of ears is a great way to uncover potential issues that you were unaware of. Take and apply all constructive feedback.
Remember, your friend is here to help you improve the script, not to criticize you as a person. Writing a good ceremony script is about the couple, not about your writing skills. The more you open yourself up to constructive feedback, the better your finished script will be.