In my opinion, I would go by the full moon or go by the waning moon if I was using the phases.
It's more just a personal preference than the moon phases. For instance, some don't go by the moon, they go by the sun or clock. Some use them all or none of them.
Generally, when something diminishes or moves down, things are sent, banished, or cleansed. And while it rises or fills, things are replenished or brought to you. At the highest point, any spell or ritual can be done or divination and reflection happens. You can apply this (or not) to any spiritual working.