How does Mark Twain get his message about slavery across to readers in 5 ways?

Huck is different than other whites including Tom. He sees Jim as a person, not as an escaped slave. Much of how Twain comments on slavery is through the character of Jim and his relationship with Huck. We understand the pain Jim feels being away from his family. We see Jim as perhaps the most sympathetic character in the book. Christian values come to him naturally while whites seem rather hypocritical and mean spirited. We see the damage that slavery does to families and individuals. The whites who claim to own these slaves are either ignorant as to what they are doing or simply cruel.