For the first lesson, I would gauge their level by giving a 45mins test. Based on that I can then move on to the weakness of its basic skills like: Mental Mathematics or Algebra. Then a 30mins lesson on the specific topic and another 30mins of questions and exercises. I have done this for almost 2 years and because of this I was able to help my students better themselves through improving their basic mathematical knowledge so that it can be implemented into more advanced topics. All of my students have improved by an average of 1 whole grade.