Don't know where to start? Think about your topic. Which national or international organisation is likely to have collated and published statistics on that topic? Go to their website and check which datasets are available.
On this page we have provided several links to sites that allow you to access statistics.
Something that you have to bear in mind when searching for data is that the most recent statistics on a particular topic may be several years old, or they don't go as far back as you expected.