Use charters to focus your exploration: "Explore the checkout flow with expired payment methods for 30 minutes." Structure prevents aimless clicking.
Look for: session-based test management, charters and time-boxing, note-taking during exploration, risk-based area selection, heuristics and mnemonics (SFDPOT, FEW HICCUPS), and converting findings into actionable bug reports or automation candidates. Best candidates explain why exploratory testing catches things that scripted testing misses.
Distinguishes senior QA from junior. Candidates who dismiss exploratory testing as "ad hoc clicking" do not understand modern testing. Those who can structure and report on exploratory sessions demonstrate craft.