The first step toward being a successful student is to go to class. Of course, being on time is part of the package. It is important for you not to miss anything that is being presented, but there is also the consideration of your classmates and the professor.
Walking into a classroom late is a great distraction. You are cheating yourself of important instructions, but it shows total disregard for others. Of course, unavoidable "stuff" happens occasionally--that's life.
When being late becomes a habit, you lose credibility and in many classrooms it will affect your grade. Don't lose your integrity as a student. Do the right thing no matter what.