Gate checked like a stroller. My guitar was waiting for me in the jetway as I exited the plane. I guess that was the colored tag - I just made sure I would be able to get it when I got off the plane.
I don't allow it to go though the baggage conveyor belts!
I was flying United - so I followed their rules and brought the guitar in a TSA approved SKB hard case. In general they were very nice about allowing a full sized guitar case on the plane. Other folks I've traveled with have brought a Taylor Baby guitar or the 3/4 size Fender in gig bags and had no problems getting them on the plane as well. These are all regular 737 or larger planes though. I've never traveled with the guitar on a smaller regional jet or turboprop.
This is the case I used - it is a regular sized hard guitar case.
http://www.skbcases.com/music/produc...set=&c=83&s=75