Here are three standard cards from the English Bridge Union.  They are all in word format so you can download them to your own computer and edit them as you wish.

Discussing and writing up a convention card is a great way to sort out partnership understanding and agreements.  I would recommend that players of all levels have a go at it.

Did you know that convention cards are compulsory if you are playing in a masterpointed duplicate.   Partnerships must have an identical card which should be offered to the opposition at the start of the round.