One method Austen uses to create interest in her characters and their marriages is to develop conflicts between characters based on inner character traits. For instance, Elizabeth and Darcy are plunged into conflict because of their pride: her pride makes her reject Darcy because he is not moved by her beauty enough to dance with her; his pride makes him haughty and arrogantly reserved at the Meryton ball. Another example is the conflict between Charlotte and Elizabeth on the topic of marriage and on Charlotte's choice of accepting Collins in marriage.
"[It] is better to know as little as possible of the defects of the person with whom you are to pass your life."
"You make me laugh, Charlotte; ... you would never act in this way yourself." (Chapter 6)
Another method Austen uses is to develop characters whose traits oppose each other though without conflict. For instance, Bingley and Darcy have oppositional traits, though no conflict, because Bingley is willing to see the best, put himself forward amongst strangers, and accept people's goodness on first acquaintance. On the other hand, Darcy thinks his actions as a scrupulous and moral man will speak on his behalf and that he does not have to inconvenience himself with goodwill to people he meets. Colonel Fitzwilliam's character traits are also oppositional to Darcy's allowing Austen to give her point a double edge. Another example is Jane and Elizabeth, whose character traits are oppositional and without conflict.
[Darcy]; "I have been a selfish being all my life, in practice, though not in principle. ... [taught] taught me to be selfish and overbearing; to care for none beyond my own family circle;..." (Chapter 58)
A third method is that Austen develops such important villains who cause such grief and trouble. For instance, the most prominent villain is Wickham whose name even declares him to be villainous! He causes extreme pain and difficulty for Darcy. He has also, before the story began, caused near-disaster for Georgianna Darcy. He nearly causes unhappiness and sorrow for Elizabeth by nearly winning her heart; fortunately he is dissuaded by her meager fortune. Miss Bingley can be thought of as a villainess in relation to Jane, who has her heart weighed down and saddened by Miss Bingley's ill treatment of her. Lydia might be thought of as a villainess in relation to the Bennet family as she is very nearly their downfall.
[Elizabeth]: "My younger sister has left all her friends--has eloped; has thrown herself into the power of--of Mr. Wickham. They are gone off together from Brighton. You know him too well to doubt the rest." (Chapter 46)