We just got the companion pass, and it's great. There are a lot of ways to do this; here's what we did:
-Applied for and received two different Chase Southwest credit cards when they were offering a 50,000 point incentive if you spent $2k in the first few months.
-Both cards were in my wife's name (you can't combine points from two or more people to count toward the $110k requirement). She took one and gave me the other. . .we both dutifully charged our normal expenses to the cards, totalling about $2500/points each. That got us up to 105,000 points.
-We then transferred enough MR points from her account to Southwest to get the additional 5,000 points. They don't transfer 1:1; I think we had to transfer about 15k MR points to get 5k SW points.
-About a month later, we received the companion pass in the mail and we're ready to roll. The earlier in the year you do this, the longer it's valid. . .it's good for until the end of the calendar year in which you earn it plus the next calendar year.
-With kids and grandchildren scattered around the Southwest system, we figure we'll probably use it five times a year. If the average cost of those flights is $250, that means we'll save $2500. . .even more if we actually use some of those 110k points to pay for flights (you can do that, too).
-When my wife's free ride ends in 2016, I'll do the same thing. If this wonderful deal still exists!
Good luck. . .lots of ways to skin this cat. A wealth of info at ThePointsGuy.com.
