The xǐng reading is mostly bound — it lives inside compounds (反省, 内省, 省亲, 省悟) and classical lines like the Confucian 吾日三省吾身. You rarely meet it as a standalone verb in modern speech.
memory
Mnemonic: with the eye (目) wide awake, you 'wake up' to a fault — that's xǐng (same root as 醒, to wake). When you squint the eye narrow to save effort, that's shěng.
Bottom indexing radical 目 (eye) — pictograph rotated vertically from a horizontal eye-shape. The eye doing the inspecting in 省's original 'scrutinise' meaning. Same radical groups vision chars: 看, 眼, 睡.
Top 少 (few, little). Compound ideograph: 'narrow the eye' or 'see less' — the original sense was to inspect closely by squinting, then to examine or scrutinise. From 'examine' it extended to an administrative division (a region under inspection) and to economise (use less). Faintly phonetic too (shǎo → shěng).
