As I do not reguraly photograph events I do not advertise it at all. However, this is what I do when I am shooting at an event. In fact, this is exactly what I am printing for a Bat Mitzvah I am shooting in May.
The front of the card I will be giving away should have your company name, and at least a website. I prefer to not include a phone number or email address I want people to visit the website and see my portfolio. I also include some of the things I like to shoot: Portraits, Headshots, etc…
On the back of the card I place a label which I make in Microsoft Word on Avery labels. I make sure to have an exact URL to the event and not a generic one.
example: njphotographer.net/jobnamehere versus njphotographer.net
Here is a typical label I would create
Thanks for reading