In the past, before all this online check in started, we'd just go to he check in counter and give them our passports and they will print out the boarding pass for us.
Not all airlines practice online check in. Usually you can just search their website for the online check in page. Some airlines online check in are quite messy and not user friendly too. Different airlines have different kind of online check in. Airasia is by far the earliest that I know you can check in (2 weeks before) while most are either 48 or 24 hours before flight.
What you need to do (and what ppl all over the world flying have been doing all these while):
- arrive at the airport 3 hours before flight
- check which check in counter your airline is at
- queue up to check in at the counter
- provide your passport and booking details (if available) to the staff behind the counter when it's your turn
- the staff will check your booking, you can then ask questions like "is the flight full?" or "Can I get a window seat?" and so on
- the staff will tag your luggage and you say bye bye to it as it moves along the conveyor belt
- the staff will present to you your boarding pass and explain which gate you have to go to and what time is boarding time
- proceed to immigration and customs and then duty free shopping
- go to gate, show boarding pass, board flight
Certain airports (I know mostly are Indonesia and smaller Philippines airports) do not include the airport tax into their flight ticket but majority of the airports do now. Just prepare some cash to be safe. Sometimes info on the internet could be outdated. You won't know until you go there yourself.
You will soon see it's a very easy check in procedure at the counter

no hassle at all