I took my time writing mine. We are reading our personal vows to each other during our first look and will do traditional vows during the ceremony. For my vows I took about a week writing them and will probably revise them multiple times before our wedding day. I want to make sure I'm going to be saying everything I want to say to him. I started by bullet pointing things I wanted to incorporate like things I'm promising to him and I also included some inside jokes as well, then I wrote it out in a way that flowed together and made sense.
I'd say stay true to who you are as a couple. We're a funny couple who joke and prank each other all of the time, but can get serious when we need to. I know his vows are going to be serious but funny, much like mine are.