Remember, the exchange of vows is one of the key reasons for your wedding day (whether it's public in a wedding, or private in an elopement), and the vows are supposed to last as long as you do. So I recommend that you put a lot of thought into what you want to promise and how you want to promise it. I expect that the memory of exchanging your vows will sustain you through both many happy days and tough times - and personally, if you are working with us, of course, I'm going to mail you then in your final ceremony, and email them to you on your first anniversary as a reminder. So I recommend that you take time to think about them and do them the way that fits you, your partner, and your relationship.
I think good personal vows answer these two questions:
How do I feel about my life partner, and why have I chosen him/her?
What promises do I want to make for our life together?
So, most vows have a combination about why this is the person they love and have chosen, and what they are promising each other. It can be as serious or as funny as you want, or typically a combination of both, but it should represent you and your relationship. They should be genuine, and absolutely yours!