A number of threads have been started by members asking for guidance on which frequent flyer mileage program they should join.

After emails with the moderators, in order to help users, we have started this thread to allow people to post their requests for information here and to allow other people to offer assistance-advice-opinion.
List of frequent flyer programs from Wikipedia

Best Frequent Flyer Program for you?
The answer to this question depends very much on your personal travel profile and objectives.
- what is your definition of best?
- do you value miles/points (or equivalent) for redemption over gaining status?
- do you fly enough to gain any meaningful status?
- what do you want to use the miles/points for (award, upgrade, hotels, what ever)?
- what sort of flight award is of interest (destination, class of travel)?
- are you interested in topping up by paying cash for miles?
- which airline and where do you normally fly?
- are you primarily a leisure or business traveller?
- where do you live?
- do you have other ways of earning points in the various programs, e.g. credit cards, shopping, etc,?
- etc, etc, etc
(above copied in part from a post by dunk)

There is a big difference between a frequent flyer and a frequent spender getting frequent flyer miles from a credit card. For questions about which is the best credit card to sign up for, to get frequent flyer miles, please do not post here, but refer to other threads on this topic. Credit Card Programs click this link and Which Forums Relate to Credit Card Topics?

Similar sticky threads
If you are sure a Star Alliance or OneWorld Alliance or Skyteam airline FFP is for you, please post in those forums, as more Star/OW/Sky experienced people are likely to answer your question.
Star Alliance forum Need advice on which *A FF scheme to join? - please post here
OneWorld Alliance forum Deciding on a Oneworld Frequent Flyer Program? Help is here.
Skyteam Alliance forum Which ST program should I sign up for?

Questions
For members asking for information, to help people to assist you, can you please provide:
(1) What is most important to you in a FFP?
(upgrades on travel, priority services when flying the airline, extra baggage allowance, good award redemption rates, better award access, free - discounted lounge access, etc.)
Reply:
(2) How many miles do you usually fly each year & in what class? How many flights/sectors?
(<25000, 25000-50000, >50000 miles - <25, 25-50, >50 flights?)
Reply:
(3) What types of fares do you usually buy ?
(First, Business, Premium economy, Economy, cheapest)
Reply:
(4) Can you choose your airlines and/or class of service? Airline most flown? Do you travel for work and/or pleasure?
Reply:
(5) Which routes and airlines do you fly most often
(US Domestic, Transpacific, Kangaroo, in Asia etc)
Reply:
(6) What is your home airport?
(SFO, SCL, London LHR, HKG, Singapore SIN etc.)
Reply:
(7) Do you have FFP status of any kind in an airline? What is it? Do you have any miles banked in a FFP?
(AA Executive Platinum, UA 1K, LAN Comodoro, etc)
Reply:
(8) Preferred Airlines
Reply:

Major airline alliances are
www.staralliance.com web site and the Flyertalk forum Star Alliance
www.oneworld.com web site and the Flyertalk forum OneWorld Alliance
www.skyteam.com web site and the Flyertalk forum Skyteam