Partially because I did this for Bourne and thought it would be a good thing to do for Orlando as well, and partially because it gives me a reason to talk a bit about him and Sam, I now present you with...
In general
Orlando is not social by nature. He puts effort into trying to be a decent, reasonable person to most of the comm. To a certain extent he's practicing social skills here, and it is slowly paying off in real life. The reason he's quite polite in many cases (unless you bring out his snarky or heroic sides, the former never being very far from the surface), is because he doesn't just talk to people, he usually has to think about it first, resulting in him saying things that he decides would be nice. Maybe it's because of this politeness, or the fact that he takes a lot of things seriously, or that he's actually something of a prodigy, or maybe just the fact he's been through hell, but he tends to gravitate to people older than him for most conversation. You can judge how comfortable he is with you by how often he makes some sort of joke (usually sarcastic). Jokes and comfort are directly related (when the fun isn't instigated by the other party, I should point out).
And in case you couldn't tell, he genuinely wants to be helpful. Like Sam said in Sea of Silver Light, he wants to be good.
...But that doesn't mean he won't mock you if you're stupid or annoying. Or if he just doesn't like you (note how in spite of the fact that he takes the threat of B seriously and will help stop B from murdering people, he'll also make fun of B to B's face). Honestly, you're asking for it.
Specific Groups
Orlando has a marked big brother streak. He likes kids, and will look out for them whenever he can (probably because he stopped really being a kid when he was around 9, if not earlier). This also extends to people who are child-like. He also enjoys just being completely silly sometimes, and kids allow him to do that.
There are a number of things that will get you instant sympathy points and cause him to give you the benefit of the doubt for a while. If you're a hacker, seriously ill in some way, are in some way "not real," or are a Lord of the Rings fan.
Likewise, there are things that instantly count against you. Killing people being the biggest. Also, holding yourself to be "better" than "normal people," threatening kids in any way, and insulting The Lord of the Rings.
Individuals (limited to those on DDD)
Sam: The only people in the world as important to him as Sam are his parents. No offense meant, but he could live without the friends he's made on here. He'd break down without Sam. She is the only person he is completely comfortable with. They can tease each other and do whatever and still know the other will be there. She'll be there to keep him practical. They get each other. In the end, he doesn't think he'll ever understand anyone else the way he does Sam, and...he doesn't think he'll trust anyone else as much either. But he doesn't have to. Because he has Sam.
LotR people: 8D! ♥!
...You know what? There are too many I feel I should put here, and it'll take ages, and I won't be happy with it for some reason or other. So...
THIS IS ALSO THE RELATIONSHIP MEME. COMMENT FOR ORLANDO'S FEELINGS ON YOUR CHARACTER(S). My other characters as well, if you say so.