My apologies for asking what has probably been asked a million times, but I could really use some help. And if this is in the wrong place, please feel free to move it!

I'm fairly a inexperienced traveller and I have never used any frequent flier program. I'm living in South Korea now, and about to fly back to the US to visit friends and family. I would like to join a mileage program but I am a bit lost as to which one is best.

I don't know what information is needed to help me out with this, so I'll just give you some basics. I will be travelling around the US for about a month and half and then going back to Korea. I plan to visit California (SF, LA, and maybe spots in between), Vegas, Minneapolis (my hometown!), New York, and possibly Vancouver.

I'm mostly interested in status, I think. I just want to be treated well when I fly. The one business-class flight I took to Vietnam was incredibly pleasant and I'd like any or all of those perks again. Free flights would be nice, but I'm suspicious about how easy they would actually be to get, so that's not my priority at the moment (but could change).

Thank you for any advice you can give!!