I agree that it depends on how I'm feeling. Usually I go in, sit on the couch, cross my legs and am relaxed. If I get real confused or an dealing with some emotions, I will normally run my fingers through my hair or fidget. When I'm extremely interested, I usually cross my arms or bring my hand to my mouth in a studious pose.

I do have a terrible habit learned from managing people that has never left me. I will replicate the position a person is in. I had read a book years ago called "how To Read a Person Like A Book". Quite a lot if it was interesting and it helped me be on the same level and relax them while speaking to them..I.e. Sitting on the same level as them, so you aren't dominant. Replicate there sitting position and there gestures to make them feel more comfortable. If worked so well, that it comes natural for me. Crossed arms can mean they want to get closer to you and the discussion, or it can mean they are no longer willing to change their bind and they are 'blocking' you. Very fascinating book.