How can I tell whether an SMT/SMD capacitor is oriented with plates horizontal or vertical?

• You can buy specially marked ones from ATC (American Technical Ceramics, and now owned by AVX, which is in turn owned by Kyocera) if you want to do this.
• Or simply choose capacitors that are not square in cross-section, so the orientation can be distinguished even without markings.
• Some datasheets have pictures that help if the cap is thinner.

#PCB Assembly