This template for Word creates a table with 3 columns and 4 rows per page: 12 "cards". The table is set up so that the page has no unused space. When you print your cards, they will all be the same size, and there will be no margin to trim at the edges of the paper.
Simply fill in your desired text inside the table cells and print. If you want to create more than 12 cards, then simply insert rows into the table.
To install this Word template, save it to a permanent spot on your machine. Then, in Word, go to File\Options\Add-ins. In the "Manage" dropbox at the bottom of the screen, choose "Templates" and press Go. On the next screen, press "Add.." to add this file.
To create a file based on this template after you have installed it: in Word, choose File\New. Then click on "Personal" and select this file.