Setting standards and expectations
It's always easier to give them some slack later.
If you don't show your in charge you'll never be able to. Start out firm and if they deserve it you can lighten up.
Your approach to the first class setting is very important. You mentioned,"start out firm and if they deserve it you can lighten up". It is important to set the tone for your class interactions. You want to create an environment of mutual respect. Being serious about classroom conduct and expectations is one way of accomplishing this goal. Clearly communicating requirements, eliminates problems later on... I especially agree with having the students sign the syllabus and even asking them to refer back to it if they have questions about expectations and requirements. This will be the final decision maker.
Harriett Russell
I agree. If an instructor's first impression is not a take charge demeanor from the moment they meet the students, they will never take charge. Students know what kind of teacher they will have from that first impression. I also, agree that after setting a firm demeanor, students will know who is in charge. This will give the instructor enougnt time to get to know students, and be able to work with students who are really deserving (hard working and want to learn)when they need a little slack.