Check-in requirements

We all aware that check-in requirements vary especially if you travel internationally. Do you have any idea what are the check-in requirements for international travel?. Thanks.

Basically, when you check-in at the airport, you will be needing you passport, you ticket or the receipt of your ticket. In some airports, you are required to show off you VISA. So, prepare this items. Are you aware of some restrictions for carry-on objects?