Pandemic 2 is not a simple game, but it is certainly challenging and it will become exciting once you figure out what you need to do.
First, you have to choose between the realistic and relax mode. The first option will make the game longer and you will be able to add various traits. If you choose relax mode, finishing Pandemic 2 won't last as long as realistic mode and some traits will be missing, but you will still spend at least 30 minutes until you finish one round. You need to choose between a virus, bacteria and a parasite. You will see a list of advantages and disadvantages for each of these options. After you set a name for your new disease, you will get a map of the world which will show you exactly what's happening everywhere on the planet. You will gradually earn evolution points which can be used in the disease screen for buying symptoms, resistance traits and transmission modes. You will get a short description for each of these options and you need to figure out if your disease will be visible and deadly, invisible but less efficient or a combination between these options.
Creating a perfect strategy in Pandemic 2 is crucial because the humans will eventually start creating a cure and your disease might not be able to infect and kill the necessary amount of people for a high score. The goal is to make the human race extinct, but this will be difficult.