Real SkyBus to Southern Cross Station costs $20 one-way with proper uniforms and designated pickup points. Fake drivers approach offering 'express hotel service' for $35-40.

Look for official SkyBus counter near Terminal 1 exit - they have blue signage and scheduled departures every 10-15 minutes. If someone approaches you directly saying they're 'faster than SkyBus', walk away. I fell for this my first time because jet lag makes you trusting and the pronunciation of 'Tullamarine' still confuses me!