An example would be "Daytona Beach automated information November, time 1455 Zulu, winds one two at one zero, gustin one five. Temperature 29, dewpoint 21, altimeter three zero, zero two. Few clouds at 3,200, scattered at 4,500. Tower 500' 3/4 of a mile off of runway 7L
unlit. Southeast ramp is closed. Follow all hold short instructions. Tower is 120.7, departure is 123.9. Contact 119.3 for Clearance, say you have information November".
After start up you listen to ATIS. Then you contact Clearance Delivery and say for instance "Clearance Delivery, Cessna 297ER requesting northbound vfr at 3,500' with information November" for acceptance of your takeoff requests. If they approve them, you contact ground for taxi requests and instructions. When holding for takeoff, you contact tower for takeoff request and instructions. After departing, you contact departure, and then they hand you off accordingly.
The ATIS is used at busier airports to alleviate radio congestion of the tower giving you altimeter settings, winds, clouds aloft, and such things as taxiways and runways inop or closed. This way, you get general airport info by an automated system that is updated hourly, and when you call tower, by saying you have "information Tango" they know that you already have that said information, and can proceed to flight specific requests and instructions.
[Edited 2005-03-07 08:18:06]