Top lawyers identify a single cause of action by systematically mapping facts to legal elements: they start with a fact-gathering phase (documents, timelines, witness notes) to create a chronological “fact matrix,” then break down each potential claim into its legal elements and test whether those elements arise from the same transaction or set of operative facts; next they run a joinder checklist (parties, reliefs, common issues, and potential prejudice) and perform a legal-issue clustering exercise to group claims that share material facts or legal questions; practically, they follow step-by-step best practices — interview the client thoroughly, prepare a cause-of-action chart linking facts to each claim, peer-review the pleadings for omissions, run conflict/preclusion checks, and draft a unified plaint that explicitly ties each relief to the common factual core — thereby ensuring claims that belong together are joined and distinct causes are filed separately.