Students who are new to statistics tend to find it tricky to remember which test to use under which circumstances. The following diagram is intended as a decision aid only. There are many many more statistical tests that are not shown here, but these are the basic ones most commonly taught on psychology courses.
Even if you end up finding out that you need a more complex or niche statistical test, an aide memoire like this can still be useful if it reminds of the relevant keywords to search.
Remember, always check the assumptions of the test you choose.