Help me figure out how to properly express milk, I'm very afraid of tr…

Help me figure out how to properly express milk, I'm very afraid of triggering lactation. I want to make a milk reserve for an emergency. I plan to express by hand and with a breast pump. 1. When should I express milk? (after feeding or before, after how long?) 2. If I only express one breast, then which one did the baby last eat or full? 3. Which breast should I start feeding from if I expressed from one (if I expressed from two, it's clear by feeling).