All of these approaches are useful in literature searches. Often you will use all three approaches for the same search topic.
Use this strategy in preliminary searches, or when you're less familiar with a topic. With this strategy you can look at different facets or aspects of your topic.
Use this strategy for well-defined (clear and focused) search questions. Plan on repeating your search with modifications so you can find more literature.
Use this worksheet (.xlsx file) as a planner.
Citation searching is another method to find articles on a topic. When you use this approach, it's important to think about alternative versions of names and citations.