This is a quick tutorial that will help you to make your way through the first steps of computational chemistry using Gaussian 09W software (G09). The tutorial is oriented to beginners and describes in detail the most used calculations done using G09. However, the theoretical basis of these cal- culations will not be covered here. If you are interested in understading the details, please refer to textbooks targeting this subject. I found  and  very helpful, and strongly recommend to take a look at these wonderful books.