I've interviewed dozens of controls engineers over the years. The ones who get hired fast all have the same 5 things locked down before they ever touch a real panel.

1. Ladder Logic fundamentals — not just "I watched a video." You need to write XIC/XIO/OTE logic from scratch and explain WHY a rung works the way it does.

2. I/O addressing — knowing the difference between local and remote I/O, how slot-based addressing works, and how to read a wiring diagram to map physical inputs to tags.

3. Timer and counter instructions — TON, TOF, CTU, CTD. If you can't build a basic sequence with timers, you're not ready for the field.

4. HMI basics — how to create screens, link tags from your PLC project, build navigation, and design alarms. Most new hires freeze when asked to build a simple HMI screen.

5. Troubleshooting mindset — the ability to go online with a PLC, force I/O, monitor tags, and systematically find what's wrong. This separates button-pushers from real engineers.

If you're trying to break into automation, nail these 5 things first. Everything else builds on top of them.