21 is a milestone age for a majority of young people especially because it is when they are allowed to legally indulge in some things like alcohol. At 21, someone feels like they are finally a grown up therefore the words used in the card should reflect this. At this age the person most likely has a great sense of humor therefore funny words that are related to beer can be used.

To get more ideas about the appropriate words to use in the card, you can write down all the reasons why the person is important to you. Use the person’s age to determine how many reasons you will come up with. The reasons do not even have to make sense or have any significance therefore they can be as silly as you like.

Come up with a poem that suits the person celebrating the birthday and use it in the card to make it seem more personalized. Messages that are related to parties also make great messages for a 21st birthday card. If the person likes to use certain words frequently, you can mention them repeatedly in the birthday card and even make some witty remarks about them.