The Deck Shield Rule is a special rule often used in competitive games, which states that illegal cards must always be suckboxed immediately. This effectively means that suckboxed cards stay in the suckbox and in the case of a rules change, players can't use overpowered cards that were created before the rules change and rendered illegal by it. This also prevents the Revivification Gambit, a degenerate tactic in which players obtain from the Suck Box ridiculous cards (i.e. I Win Cards and You Lose Cards) and then use them to flatten the game. As such, the Deck Shield Rule is recommended.
Another recommended rule is the 1000 Point Limit. Others can be found under Competitive Rules.