Twelve factors, abridged
The twelve factors started as a checklist scribbled on the back of a failed summoning circle. They have since become the baseline for any incantation that has to run in more than one realm. This guide covers every factor in depth; here are the three that cause the most trouble.
Keep config in the environment, not in the spell. An incantation that hard-codes the full moon will not cast during a waxing crescent, and nobody will remember why. Treat familiars as disposable: a familiar that cannot be restarted without a ritual is a single point of failure with whiskers.
Finally, keep staging and production as similar as the laws of magic allow. Every incantation should pass through a staging realm before it is promoted, and the closer that realm resembles production, the fewer surprises reach the village.