Using the traditional serological tests and the most novel techniques for DNA fingerprinting, forensic scientists scan different traits that vary from person to person and use the data to include or exclude suspects based on matching with the evidence obtained in a criminal case. Although the forensic application of these methods is well known, the procedures and techniques used to obtain these results are not so well studied. Here, we report a laboratory exercise aimed to familiarize the students in several of the methods and markers employed for people individualization. With this exercise, students have to characterize themselves and an unknown sample according to the following characteristics: ABO blood group, presence or absence of Y chromosome, and their polymorphism for a variable number of tandem repeats (VNTR). This exercise has been originally developed for students of the course "Techniques in Criminology" within the Bachelor of Criminology. Although the schedule and procedures have been addressed to students who are faced for their first time with a laboratory of molecular biology, the exercise can also be adapted to students in more specialized courses and studies. (Contains 3 tables and 4 figures.)