"Be" verbs deprive a sentence of action and nuance, but students often focus so hard on the rhetoric and grammar of their argument that they don't realize the lack of diversity in their sentence structure. Rather than pointing this out individually, write a sample paragraph with numerous "be" verbs, such as "I am in a room. The room is white. The walls are straight." Have students read the paragraph aloud, discuss the inherent problems within and ask students to eliminate all "be" verbs. Doing so encourages creative diction and, more importantly, transitive verbs.
Students unfamiliair with college writing might use "common knowledge" as supporting evidence. This can range from "it's in human nature to be violent" to "everybody knows that marriage is more likely to end in divorce than happiness." Though these statements may carry a hint of truth, the converse can be easily argued. If you see this in numerous papers, excerpt each example and distribute several to students. Have them think of ways to support the statement or incorporate more concrete data. It's a good opportunity to introduce students to the computer lab or library to heighten their research skills.
Transitions can prove challenging, even to seasoned writers, so imagine how daunting they can be for freshmen. To make them less intimidating, distribute two index cards to each student and ask them to write a silly noun on each card. Place the cards in a bag and tell students to pick two cards, write a transition connecting them and read the transition out aloud. Ideally, most of the transitions will be humorous, making the process of writing transitions less terrifying.
Though more common in creative writing classes, the Elegant Corpse, a traditonal writing exercise, is an example of what happens when sentences don't follow in logical order. Ask each student to take out a piece of paper and write a sentence at the top. To modify the Elegant Corpse activity, fold the paper so the sentence isn't visible and pass to the next student. Continue until each paper reaches its owner. Read aloud and segue into a discussion about the importance of sentence continuity.