First off, you need to be sure that the person performing your ceremony will allow you to create your own vows. I know what you are thinking, why would you pick someone who doesn't allow this? Some places of worship, or churches don't allow you to do this. Be sure that you can do this prior to booking any ceremony space or officiant if this is something important to you.
You should write your vows about a month before the big day when you are in a relaxed state of mind (if that's possible while planning a wedding). Writing your vows a few days before the wedding may make it feel very rushed. You want the vows to be as genuine as possible. I often don't suggest practicing the vows a ton before the wedding because they tend to sound scripted or even worse, they don't sound genuine. But you should absolutely rehearse them a few times, and practice looking up while reading. There is nothing worse than avoiding eye contact with your partner while saying your vows.
Be sure to talk to your partner ahead of time and set out a few ground rules for the vows. Nothing embarrassing should be mentioned as part of your vows. Keep these stories for the speeches and toasts. Set a word limit so you are both on the same page. Talk a bit about the tone of the vows, are you both going to be humorous or serious? It would also be a good idea to set a format for the vows. An example of this would be that both parties should include two promises that they will say to each other, or both parties will include one thing that they are looking forward to in the future.
Google templates to see what you like together, borrow poems and quotes from your favorite movies or books. Try to create a balance between your promises and your life experiences. Make it personal by adding a few stories (how you met, when you fell in love, how he/she proposed), not every wedding guest will know this stuff about you two.
When writing out your promises to one another make sure they are realistic. You are promising these things for the rest of your life. Rather than saying "I promise to make you soup every time you get sick" try "I promise to make you soup when you get sick". I know this may not seem like a big deal, but don't make promises you can't keep for the rest of your lives together.
It is also completely ok to use a bit of a template for the vows. Consider adding something like this as a starting point and customizing it, and adding in your own stories/promises:
"I take you as you are, loving who you are now and who you are yet to become. I promise to listen to you and learn from you, to support you and accept your support. I will celebrate your triumphs and mourn your losses as though they were my own. I will love you and have faith in your love for me, through all our years and all that life may bring us."
It's always important to send a copy of the vows to your officiant or planner. If you lose or misplace them, you would have your bases covered.
Once you are finally done writing out your vows, remember say them out loud. Decide how you are going to say them or which words you are going to emphasize. Pause when you assume you will need to and have fun. The ceremony goes by so quickly, and it is truly the most important part of your wedding day. Relax, enjoy and make everlasting memories.
Photo Credits: Sugar and Soul Photography