There is also a group formation option. It is on the top right corner of the screen (on the left of the timer). You must have more than 1 unit selected in order to use this option. The short cut for these formation are numbers 1 - 9 (on the main section of the keyboard). Very handy sometimes.

You can also assign group number. Ctrl + Shift + # (0 - 9) to assign and Ctrl + # to call.