Quote? Well, the best way to figure that out is ... Look at the ending pictures!
(tell me if these images don't show up for you, I direct linked from the cavestory.org site)
First and most importantly, Quote acts human enough to fool most people that don't know exactly what they look like. Even Misery and Balrog who has fought with similar robots like Q and C couldn't recognize him as a robot at first.
Quote is the easy to talk to type. He says the right things, but he doesn't stand out. Somehow he earns everyone's trust.
In the beginning he is probably pretty blank in his objective.
He takes the gun, falls on his face; and I guess is just wandering aimlessly.
Only seems to target anything that is hostile towards him.
He must have recognized King as friendly, and said something nice; since King opens up to Quote immediately, even though he clearly thinks of Sue as an outsider and has a grudge.
Whatever Quote says apparently earns him more trust than Sue was able to all the time she was there!
....
In the beginning he does not take sides. He sees Toroko getting taken and does nothing. He sees Sue taken and does nothing.
Does he act good or bad? I don't know; that's up to you. Do you help Kazuma? Do you tell Curly you will kill the Mimigas?
It isn't until the Labyrinth that Quote decides his path. He has probably gathered enough information to figure out what kind of robot person he wants to be.
Typically pretty friendly, but probably quieter (but not mute!) than Curly. There are a few dialogues where Quote must speak for it to make sense, but it usually shows Quote speaking by : "....." Look for spots that say "......" and that's usually where you say something. [That and at the beginning and end of conversations]
Personally, I always thought of Quote and Curly to be kind of like the characters :
Chrono and Rosette from the Chrono Crusade anime...
Chrono is a bit more serious, brooding, friendly, has a dark side, but is quite the warrior.
Rosette is the outspoken, smiling, strong-willed character, has seen dark things, but quickly finds that smile with friends.