You need to choose the state standard in which drawing conclusions fits.  My assumption, upon reviewing the Indiana State Stadards for 6th grade, would be that it fits into this one:

EL.6.3 2006 - READING: Comprehension and Analysis of Literary Text - Students read and respond to grade-level-appropriate historically or culturally significant works of literature. The selections in the Indiana Reading List illustrate the quality and complexity of the materials to be read by students.

Drawing conclusions about Brian would be considered an analysis of a literary work.  So your objective - which should be measurable - would concern drawing conclusions as literary analysis.

Example: 

Objective: Students will be able to use critical thinking skills to draw conclusions about Brian's actions as connected to his character.

Measureable Assessment Indicator: My students will draw three conclusions about Brian's actions that prove he has changed as a result of his surroundings.

To plan your lesson, make sure you tell the students what you are expecting them to learn and what you expect the outcome to be. 

Then you model.  Your model should be you drawing a conclusion, either about Brian or a character in another familiar story, and showing how it relates to his experiences.

Then consider reading a short passage from Brian's Winter, having students draw conclusions as a guided, whole class approach before letting them attempt the three on their own.