One way to teach students to make inferences is to teach them that there are different kinds of questions. Questions where the answer is clearly in the text, questions when you must use your own head, and questions which ask you to connect to the text.
Francie Kugelman has created these charts which students can use to identify the types of questions as well as eliminating wrong answers on tests.
Please see the Comprehension Page (accessible from general Open Court Resources) to download the form. Scroll down to “Teaching Inference.”