The first two are rather obvious, being the ex-versions of the Legendary duo Miraidon and Koraidon
When the first, second, or third chapter ability of The Tale of Tamiyo resolves, the ability will continue until you mill a set of two cards that share no card types or you mill one or fewer cards
Go to an Official Tournament Store Going to an OTS might seem like the easiest way to find people to duel with, but many don't know if their region has a store, and there are even people who don't know about official Yu-Gi-Oh
Examples are Brock's Mankey (switches the defending Pokemon, was played as an "anti-Slowking"), and Cleffa (this card was literal bajeezus since it's a 1-energy draw seven (!), doesn't require evolution, retreats for free, and even had a 50% chance of avoiding any counterattack)