The purpose of journals is to develop fluency and promote critical thinking, Journals are a positive way to encourage self-expression. They can help students explore course content and tie it into personal experience or observations of everyday life. Journals are distinguished by an informal nature, an intimate audience (often being addressed to the writer himself and no one else), and regular entries. Since journals are intended to provide writing practice, encourage writing in complete sentences rather than lists or fragments. While some journals are completely personal and can address any topic, other focus on course content and will include the instructor and peers as audience.
A caveat: don't ask students to be too personal in journals, or you may find yourself in some awkward situations. You do not want to have to comment on their most intimate thoughts or experiences, and you do not want to confuse teaching with counseling. Begin with journal assignments that develop skills you want practiced, and provide sample journal entries. Demonstrate what sorts of questions, insights, or criticisms a sample reading might elicit. Be especially careful to define (operationally if possible) terms such as "close reading," "critical thinking," "insight," or "imagination." While you may simply ask students to respond to readings or class discussions in their journals, you may also want to provide a short list of prompts for them to use if they can't think of a subject. Require that students give concrete evidence to support the opinions they give in their journals. This will help them learn to elaborate.
Collect journals at regular intervals, perhaps once early in the term, once at mid-term, and once toward the end, so you can see how students are using them and provide useful feedback. It is best to limit your responses to content. Encourage them to think more deeply about the subject rather than focus on errors. If students get the idea that correctness is paramount, they may begin to censor themselves. Fear of making a mistake can block creative and critical thinking and slow an inexperienced writer to a crawl. Comments, suggestions, and questions in the margins made as you read gives students the sense of how a reader responds to their ideas.
If responding to each journal in writing is onerous, simply check that they are being done and respond randomly to a few, perhaps picking different ones each time. Alternatively, you can have students read each other's entries, or you can read some especially good entries aloud as the basis for class discussion. Also consider allowing students to mark some entries as "Private—Do not read." Evaluate the length, but don't read the entry. This allows more freedom of expression. Dialogue journals are a particular type of journal which takes the level of response one step further. The student writes an entry, to which the instructor or peers respond. In turn, the student responds to the response.
Fulwiler, Toby, ed. The Journal Book. Portsmouth, NH: Boynton/Cook, 1987.
Reynolds, Julia, et.al. Writing to Learn in Undergraduate Science Education.
Double-entry journals are discussed at www.readwritethink.org/classroom-resources/printouts/double-entry-journal-30660.html.