Where parts go

The layout is yours to design. This skill holds the facts and checks that are easy to miss.

Before placing

• Datasheet layout sections are requirements. Where a datasheet leaves a choice open, make it and say it's your inference. If its reference design has a part the schematic lacks, report it rather than adding it.
• Fixed parts first: the outline, holes, connectors and whatever the enclosure fixes. Ask what fixes them.
• Assign pins from the floor plan, before the schematic is final. On an MCU with alternate functions, and on any connector or header whose order is free, choose pins from where the other end sits, so buses leave on the side they're going and signals don't have to cross. A pin change after placement means a schematic edit, board.py sync, and re-routing.
• Bottom side: ask before placing parts there.

Passives at fine-pitch pins

Two passives centred on neighbouring pins fit only if the sum of their courtyard widths is no more than twice the pitch. KiCad's stock courtyard widths: