What should I do to make sure my passive winterizing goes well?

First of all, lower the water level of the pool by 1/3, think of installing wintering floats in the pool and skimmers.

Think of draining the different equipments of the pool: pump, filter, heat pump, electrolyzer. Add winterization product to stabilize the water, and finally, cover the pool.

If in doubt, do not hesitate to call a professional.