My first step into this game was with the Southwest Companion Pass, which has served me well, but will be up at the end of 2017. Since WN has no alliance, I haven't had to worry about it yet, but I want to make the best decision for the future. I've narrowed it down to oneworld and Star Alliance (not really interested in SkyTeam). As an addition to the answers below - if I can bank miles to a program that would allow lifetime status at some point, I'd like to. Might as well have an end goal, right?

(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: Definitely good award redemption rates and better award access, lounges would be nice. Not a whole lot of interest in extra services or free baggage, I travel light. Credit cards in the US are a plus though, as I don't want to worry about expiring miles all the time.
(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: Less than 25k miles, hoping to fly more in the next few years with all these miles I've been banking!
(3) What types of fares do you usually buy?
(First, Business, Premium economy, Economy, cheapest)
Reply: Economy. I'd like to book business or first award tickets at some point, but can't see myself paying (as opposed to award flights) for those very often.
(4) Can you choose your airlines and/or class of service? Do you travel for work and/or pleasure?
Reply: No work travel right now.
(5) Which routes and airlines do you fly most often?
(US Domestic, Transpacific, Kangaroo, in Asia etc)
Reply: Currently, mostly domestic (Southwest CP). No "most often" routes planned in the future though, just looking to see more of the world.
(6) What is your home airport?
(SFO, SCL, London LHR, HKG, Singapore SIN etc.)
Reply: BOS (PVD too if it helps)
(7) Do you have FFP status of any kind in OW or other airline? What is it? Do you have any miles banked in a FFP?
(AA Executive Platinum, QF Gold, UA 1K, LAN Comodoro, etc)
Reply: No status, 350k AAdvantage miles and about 120k Alaska (I know it's not oneworld, but the American/Alaska relationship may help?)
(8) Preferred Airlines? Most common Airlines flown on?
Reply: No preference. I don't need a lot of frills, but of course my flight experience is somewhat limited so far.