Frequent Flyer Program - 2

1. Enrol in EXACTLY 3 frequent flyer programs, no more, no less

Rationale for doing it
There are 3 global airline alliances, Star Alliance, SkyTeam, and OneWorld. They cover most of the routes in the world. If you choose 3 airlines and each belong to one of the alliances, you can travel anywhere with mileage pocketed

Problem if you don't do it
Some people take flights that don't fit their schedule well just to earn miles in their preferred airlines. One of my friends, who's a Cathay Pacific member, picked a flight very early in the morning just for the Miles. Enroling in 3 programs avoids this unncessary compromise. If he is also a Singapore Airline member, he could have gotten a much better schedule between Singapore and Hong Kong

Exmaple of how this is done - Hong Kong as base city, with lots of traveling (>50 sectors a year) within Asia and moderate traveling (10 - 20 sectors a year) outside Asia

Preferred options depending on your routing. They should be complimentary, so if you have JAL already, you wouldn't want ANA as well
1. OneWorld - Cathay Pacific / JAL
2. Star Alliance - Thai Airways / Singapore Airlines / ANA / Asiana / Air China
3. SkyTeam - Korean Air / Delta / China Southern

Recommendation
1. OneWorld - Cathay Pacific
2. Star Alliance - Singapore Airlines
3. SkyTeam - Korean Air

Exceptions
If a lot of your trips involve the Middle East, enrol in 4 programs. 3 airlines in each alliance, plus the Emirates. It is essential to get Emirates status as it covers many routes from Dubai, a major regional hub. Separately, if you fly extensively to/from Taiwan, getting China Airlines / Eva membership helps