While the words you write are the most important thing, presentation can make it even better. Timeless Message can help you with the presentation part, or you can go to a craft store and buy a nice bottle, a couple sheets of special paper, and a bit of ribbon to do it yourself for a lot less. (Thanks to whoever pointed me to Timeless Message a while back – I thought it was on the comments here but I cannot find it.)
As to the words, give it a lot of time and effort. Write and rewrite, do not just bang something out Christmas Eve. You are trying to put your heart on paper here!