Tools of Characterization
Ros and Guil are not the two most active guys in the world, but Guil does, occasionally step up. Guil slaps the player and later he tries to stab him. Ros at one point yells at the player for being obscene, but never gets physically violent. On an obvious note, this suggests that Guil is aggressive. On a more interesting note, it suggests that, as articulate as Guil seems, he often feels incapable of expressing himself with speech and has to turn to violence. You might also note how the Player slaps Alfred the same way that the Guil slaps the Player. Does this mean the Player and Guil have something in common? Is this like when the dominant monkey goes and slaps the second in command and then the second in command takes his anger out by slapping the third in command?
Not exactly a big tool of characterization, but what does it say about the Player that he never changes out of his costume? Is he the only person in the play that is always acting or is he just the only actor in Stoppard's play who realizes that he's wearing a costume?
Again, not a huge one, but note that the Player doesn't have a name other than the Player. This is a bit like his never changing out of his clothes. Also, some etymologies trace the name "Hamlet" back to the word "fool." Does Hamlet appear more like a fool in Stoppard's play than in Shakespeare's?
Speech and Dialogue
This is a play so, yes, there's a lot of dialogue. It's complicated a bit by the fact that some of the dialogue is in Shakespeare's English and some is in modern English. It's worth noting the way that Guil often tries to frame what he is saying as a logical argument, no matter how illogical what he is saying might be (think Will Ferrell doing The Matrix 2 at the MTV Movie Awards… "Ergo… Vis a vis…"). Ros, on the other hand, tends to speak in plain terms. When he goes on his long rant about being dead in a box, one idea just spins into another. Guil wants to appear more sophisticated than the other characters in the play, but it is unclear whether or not this is just a pose.
Another thing to think about is where the Player's dialogue fits in. Like Guil, he sometimes speaks in an elevated manner as if he's trying to appear more important than he actually is: "The plot was two corpses gone before we caught sight of ourselves, stripped naked in the middle of nowhere and pouring ourselves down a bottomless well" (2.112). Is his speech closer to that of Hamlet and Claudius or to that of Ros and Guil? Is he capable of moving back from one type of speech to another?
Thoughts and Opinions
Unlike speech and dialogue, this doesn't have to do with how the characters talk, but with what they actually say. First, we notice that Guil likes to talk about his opinions – a lot. Ros may like to do the same, but he's definitely overshadowed by Guil throughout. Guil has an obsession with reality. He wants art to mirror real life, and he wants art to admit those points where it falls short (for example, its inability to portray death). Guil is concerned about the nature of existence – what he's doing and why – and he tends to seem more comfortable when there is a logic at work than when things are going arbitrarily.
Ros, by contrast, has many more thoughts than he does opinions. His thoughts are often silly, and he's not very good at reasoning through a problem, but he just honestly doesn't understand why someone would be afraid of death. His thoughts don't preoccupy him the way that Guil's thoughts preoccupy Guil.
The Player thinks that art is much like a play, and says that people should just play their roles instead of questioning everything. This makes him an interesting but tricky character to talk about because he thinks of himself as a "character" as much as he thinks of himself as a "real person."