As mitzy says its all in AMM ch 5. Phase 1 basically requires looking for skin wrinkles, popped rivets, buckles, missing fasteners, missing/damaged access panels, leaks, landing gear damage/leaks, etc especially in critical areas identified by the manufacturer. If nought found no need to go to phase 2 which requires more detailed inspection of a damaged area.
On the 747 these days there is a requirement to check all the engine pylon to wing attachments which is hours and hours of work. Gone are the days when you could do the phase 1 inspection in a couple of hours!