We've always followed the top down rule. Start with the ceiling, then walls, then floors- then whatever goes on top of floors.
That said we've not done a full gut job on a bathroom yet so that has only been for bedrooms/living rooms.
- Electrical and plumbing.
- Drywall Ceiling.
- Drywall Top half of wall. If doing tile for tub/shower, use cement-board.
- Tub/Shower pan install.
- Drywall remainder (or cement board as noted above), tape and mud. Texture if applicable.
- If doing tile for surround, redguard(or similar) for waterproofing.
- Prime and Paint.
- Shower/tub surround & Flooring.
- Entry door (if applicable).
- Vanity, Baseboard & Trim.
- Misc. (towel racks, TP holder, etc.)
Do baseboard before your vanity is "furniture" style (has legs, and doesn't go flush to wall) rather than "cabinet" style (Flush to wall, looks like a built in similar to kitchen cabinets).