Character Clues
Character Analysis
Actions
Good and bad acts speak volumes about the characters in Pamela. In the early part of the novel, Mr. B commits numerous acts of violence against Pamela (and attempts to commit more), suggesting that his moral compass needs a trip to the shop, pronto. Meanwhile, Pamela's refusal to participate in bad acts attests to her goodness and virtuousness.
Of course, this all gets a little tricky and confusing when we have to suddenly believe that deep down Mr. B was always a nice guy, but hey. It's a good story.
Direct Characterization
Rather than simply letting the characters' actions speak for themselves, Richardson (via Pamela and the editor) just goes ahead and tells us who the good guys and the bad guys are. That's handy, since those titles shift a bit from the beginning to the end.
When Mr. B first makes his evil intentions toward Pamela known, for example, she describes the transition in her opinion as such:
O this Angel of a Master! this fine Gentleman! this gracious Benefactor to your poor Pamela! who was to take care of me at the Prayer of his good dying Mother; who was so careful of me, lest I should be drawn in by Lord Davers's Nephew; that he would not let me go to Lady Davers's: This very Gentleman (yes, I must call him Gentleman, tho' he has fallen from the Merit of that Title) has degraded himself to offer Freedoms to his poor Servant! He has now shew'd himself in his true Colours, and to me, nothing appears so black and so frightful. (13.2)
Got it? Mr. B is degraded, frightful, and wicked. Sounds like great husband material.
Family Life
Familial relationships tell us a lot about our main characters. For example, Mr. B's fights with Lady Davers shed a lot of light on the underlying attitudes and (bad) habits of thought that seep into their behavior—like that they're both spoiled aristocrats.
In contrast, Pamela's devotion to her parents and their values are yet another piece of evidence that Pamela is virtuous and noble—and maybe a little too good to be true.