Passengers check-in usually starts two hours before schedule time of departure and closes 40/30 minutes before departure, depending of airlines procedure.
Inside the terminal building there are flight information display screens which advice passengers about important details such as: flight status, check-in and gate number for their flight.
Upon airport arrival the passenger reports to the check-in desk with a valid travel document and reservation number (if neceessary other required documents such as visa). At the check-in counter passenger receives boarding pass which allows to board the aircraft.
The luggage is properly marked and directed to the security check, customs control and finally to the aircraft hold.
Low-cost airlines such as Ryanair require online self-check-in. Check-in at the airport is additionally charged.