It’s important that you know your students the most you can without getting too personal. Observe their behavior and take some notes for yourself when you can.
Ideally speaking ‘equality of treatment’ supposed to work, but you will discover that some students need a different approach than others; such a more severe discipline or less than their peers. When one of the students behaves badly in class, don’t rush into judging him/her; since they might have different conditions (such as ADHD, Asperger, etc) or problems that distract them or take them to moody behavior (such as family issues- this is very common). Consider asking parents when you feel appropriate if a student has any condition you should be aware of; is better prevent the chaos than trying to fix it.
I remember that in my first year as a teacher, I had a particular student whom used to behave very lazy, and his attitude looked irritating because it seemed that he didn’t care. I remember having a discussion with his mother where I explicit said that her son was lazy. She immediately reposted it to the Principal whom talked to me and asked me to apologize; he didn’t say more. I started paying extra attention to this student because I wanted to understand his behavior; I found out that he indeed had an attention problem and his way of getting away with it gave him a look as if he didn’t care. I asked him to be closed to my desk and I started giving the class tasks one by one instead of giving him the list. And every time he finished one task, then I helped him moving to the next one.
Later that week, I had the chance to talk to his mom and I mentioned to her the process of that week and I also apologized for the previous comment. (See, parents want us to understand and appreciate their children as if were our own). She was very thankful and asked me to teach her the task plans so she could help him at home. I was happy that this uncomfortable situation leaded me to a self-discovery skill and allowed me to grow as a professional.