Every test needs to follow a sequence of actions, which lead to the function under test. It could be a certain page that a user needs to be on, or certain data that should be in the system (like registration data in order to login to the system), or certain action. State this precondition clearly in the test case. This helps to define specific steps for manual testing, and more so for automated testing, where the system needs to be in a particular base state for the function to be tested.