Step By Step - Traveling With Commercial Plane

Check your flight schedule 1 or 2 days before your flight date and arrive at least 2 to 3 hours before flight time. flight schedule could be changed or delayed without notice, so you will need to be there to heard the announcement about your flight.

Now, let's begin the step by step.

- Check in to your flight counter. you will need your passport and ticket reference number to claim your flight ticket.

- Pay airport tax at tax office. you will need your passport and flight ticket. Airport tax fee was Rp. 75,000.-

- Continue to immigration post. you will need your passport and flight ticket.

- Have your time to shop at airport while waiting for your flight. Some will need your passport or ticket flight.

- Flight check in estimation 20 - 40 minute before flight. you will need your passport and flight ticket.

- Have a nice Flight.

Once you has arrived your destination, 

- Proceed to Immigration post. you will be asked for some question and you will need your passport and immigration card (one you get in flight).

- Collect your baggage if you have baggage

- Proceed to exit door through luggage scanner.

For return flight, you could follow these steps.

- As usual, check your flight schedule and arrive 2 to 3 hours before flight.

- Find your flight check in counter and claim your flight ticket. you will need your passport.

- Proceed to immigration post. you will need your passport and your immigration card (one you get in flight).

- Have your time to shop at airport while waiting for your flight. Some will need your passport or ticket flight.

- Flight check in estimation 20 - 40 minute before flight. you will need your passport and flight ticket.

- Have a nice flight

And finally when you has landed, 

- Proceed to Immigration post. you will need your passport and customs card (one you get in flight).

- Collect your baggage if you have baggage.

- Proceed to exit door through luggage scanner.

Note : 
This was written based on my own experience from Medan Polonia (MES) to Singapore Changi International (SIN) round-trip.

If you know airport website that could provide flight schedule, that would help you much. if not, then check to your flight website.

Hopefully this would help you a lot.