In To Kill a Mockingbird, during chapters 1-3, which characters inform Scout about proper behavior?I know that Calpurnia is one charcter, but I...

You are right that Calpurnia provides a quick lesson in
proper behavior at the supper table in Chapter 3.  She scolds Scout and tells her the
way she is speaking to her "guest" is inappropriate.

But
the fact is, Scout is learning about "proper behavior" throughout the book, from almost
every character.  Whether the lessons are direct or indirect, each character she
interacts with provides a model of proper or improper
behavior.

In chapter one, her brother Jem's easy way with
meeting Dill and forming a friendship is a social lesson for his younger sister.  She
looks up to Jem.

Miss Caroline, in chapter two, also gives
Scout a lesson in "proper behavior" for a traditional classroom.  This is a lesson Scout
neither understands nor agrees with.  As a result, Atticus finishes this lesson on the
porch in chapter 3, and teaches her the infamous lesson of considering other people's
feelings.

I encourage you to read each chapter with the
idea in mind that each situation Scout encounters is a potential "life lesson" or
"behavioral lesson."  It will help you understand some of the deeper themes of the book,
as well as track Scout's growth and maturity.