If I am comfortable around someone, I am warm, bubbly, jokey, and child-like.
If I'm not comfortable around them yet, I am rather quiet, reserved, cautious, and insecure.
If I am with 1-2 friends, then I am the former.
If I am with 3+ people, I am the latter. (For example, when there was a meetup in seattle a couple years ago, i was conflicted about going because even though i really wanted to meet each of the people that were going, I knew i would be closed off due to there being four other people and possibly R, too. I wanted to spend time with each of them individually, not as a group.)

I don't talk as much irl as I write in my posts.
I typically avoid arguments, unless I feel as if someone is trying to force themselves onto me. Even then it's not so much an argument but a firm No, kind of thing. Usually I try to change the subject, though.
I am more reactive irl than proactive. Writing online allows me to practice being more assertive and proactive about some things.

Online I open up my thought processes to be viewed as its happening...followed by tons of edits. Irl i can't edit, so things come out really jumbled, lots of errors, poor word choices, lots of jumping around, and I'm sure i look pretty darned stupid. I know i do, cuz it's one of the things i've been picked on for forever. So in anything really important to me, I tend to keep my mouth shut and not talk about irl. Some of you wouldn't even recognize me as being the same person.

I tend to be touchy-feely. I like hugging hello, goodbye, or to show emotional support. Maybe an arm around the shoulders, or a light touch on the arm or hand. I also tend to do tiny acts of service, like opening doors, carrying something for them, walking them home in the dark, etc.

Thats all i can think of for now.