Effective data visualization is one of the key elements of a modern analyst portfolio. You will learn what are the good practices of making charts and dashboards, how to choose a proper visualization for a particular need and what mistakes to avoid. There also will be many examples of bad data visualizations along with the practical tips on how to fix them. Apart from that some hints where to find useful knowledge and inspiration on data viz will be given. Presentation prepared for the Kraków Tableau User Group #2.