Set the ticket before the sights
Buy ICOCA at the airport. For a Namba stay take Nankai Rapi:t; for Umeda or a shinkansen take JR Haruka. Both need a limited-express ticket. A Metro day pass covers neither. Do not study four lines while clearing immigration.
Umeda is a change; Dotonbori is night
At Osaka Station split north exit, south exit and Hankyu. The three Umeda metro stations are not one paid area. Do not spend the day inside the station. Save Dotonbori for night, walking from Namba toward Ebisubashi. USJ is its own day.
Who this primer suits
First-timers, four days or fewer, no appetite for private-rail detail. Already locked on USJ-only or Kyoto-only: jump to that guide. Do not put Umeda, Namba and Universal City on the same day.