Turn off your cell phone in a very noticeable, almost formal fashion at the beginning of each class. Instructors should model behavior that they want students to follow. The instructor should suggest that students turn their phones off, and make it clear that at the very least phones must be set to silent or vibrate. If a student has to take an emergency or high priority phone call, then she absolutely must respect her instructor and classmates by stepping out of the classroom while she's on the phone.
Make students eat their meals outside of the classroom. A student will struggle to focus on the lecture if he is chowing down on a pan pizza or using a napkin to wipe Taco Bell sour cream off of his face while the teacher speaks. The smell and sight of food can also distract other students who need every bit of concentration in order to take notes or do classwork. It might not be reasonable to ban all food and drink from the modern classroom, so an instructor may allow students to bring a drink or small snack to class, but students who bring a full meal to class demonstrate a lack of priorities.
Call on all students regularly. Teachers can prevent overbearing personalities from drowning out quieter students by not allowing students who overvalue the sound of their own voice to monopolize class discussions. For example, if a student has talked a lot about one particular subject, an instructor can politely say something like, "Dan, that's an interesting perspective you have. I would like to hear what other people think as well," and then call on or invite more quiet students to contribute. Remember that more mellow students may have something to say even if they do not outwardly show a desire to communicate.
Deal with tardiness right away. If students routinely show up late or don't show up at all, speak with them about it as soon as possible. Students need to know if their instructors are deducting points or otherwise holding missed time against them. Inform your supervisor or department chair as well. If an instructor has spoken with a chronically tardy student and informed his supervisor of the situation, then any disciplinary decision he makes will not seem rash or unfair. Remember that instructors might not have to catch up or assist students who fall behind due to their attendance habits unless school policy states otherwise.