Go to your airline counter and show your Passport, Tickets. Tell them of your preferences, such as desiring vegetarian food, a window seat, or a nonsmoking area.
They will weigh your baggage. They will ask you two questions: "Did you pack the bags yourself?" (Answer "yes" if applicable.) "Did a stranger give you anything to carry?" (Answer "no" if applicable.) Ask them if your baggage is flying to your final destination on the same airplane. The agent will give you a boarding pass with a baggage sticker and your passport/tickets back. Keep these documents safe. They'll tell you the gate number (the gate number is where your plane will arrive after landing). You should have only hand baggage and the documents in your possession at this point.
Once you enter the terminal, you cannot leave. If you've arrived early, take this time to spend time with your family or friends outside the terminal before entering.
Airport personnel will also give you a form called the Embarkation Form, which looks like this: