Wait for Regidrago to return in Pokémon GO raids
Check the current raid boss rotation and event announcements
Join a raid lobby when Regidrago is available
Defeat Regidrago in the raid
Catch it with the lowest possible CP by using a low-level account
Use a raid encounter with no weather boost
Avoid using a high-level account if you want a lower-level catch
Trade for a lower-level Regidrago if you already have one available
Use a special research or timed research reward if Regidrago is ever offered there
Keep an eye on GO Fest, raid days, and special events for another chance to get it