Common betting systems used in Blackjack include strategies designed to manage wagers and maximize potential winnings while controlling losses. One popular approach is the Martingale system, where players double their bets after every loss, aiming to recover previous losses with a single win. Another method is the Paroli system, which encourages players to increase their bets after wins, leveraging winning streaks. The Fibonacci system utilizes a sequence of numbers to determine bet amounts, increasing stakes after losses and adjusting down after wins. Flat betting is also prevalent, where players maintain a consistent wager regardless of the game's outcome, providing a more stable approach. These systems all aim to enhance bankroll management and improve the player's chances of success, though they carry inherent risks and do not guarantee profits.