Using abusive language
If the referee sees or hears any of these things, an instant penalty will be given.
A yellow card and a spell in the sin-bin are also likely.
Tackling offences
Tackling is a huge part of rugby league but it's important to know how to tackle within the laws, so as not to give away a penalty.
Once the player with the ball has been tackled and brought to ground, the tackler must release them, allowing the opposition to play the ball.
Sometimes defenders can cleverly hold down the player with the ball to stop them playing the ball quickly.
But if a referee believes a player is deliberately holding down a player in the tackle, he will award a penalty to the team in possession.
Sin-bin
The sin-bin is the bench where, in theory, all players cool off for 10 minutes after committing a serious foul or showing indiscipline.
If this happens, the referee shows them a yellow card, just like in football, but the punishment is immediate. They must leave the field straight away.
The game will continue without the player, putting their team at a disadvantage as they will only have 12 players on the field.