You have asked a very broad question, and you might find it more useful to ask a question that is more specific, for example about a certain theme in the novel or focusing on a certain character or section. However, I have included some links below to the enotes study section of this novel that should give you some more information.
I have just finished teaching this novel with my Grade 11 students, and I always try to teach it thematically, focusing on the four major themes as follows:
1) The inhumanity of slavery
2) The hypocrisy of Christians
3) Huck's coming of age
4) Nature vs. civilisation
You might find it helpful to bear these four themes in mind as you read and study the book, taking notes on particular examples from the story which highlight one of the themes. Consider, for example, the way that hypocrisy of Christians is shown through the Widow's refusal to let Huck smoke whereas she herself takes snuff. Hopefully, this will give you some ideas on how to approach the novel as a whole and to begin to analyse it. Good luck!