Roleplaying literally means having a character with a personality and playing him or her consistently.
In everyday speech roleplay (or rp in short) is used as a synonyme to emoting, writing actions that are not programmed into the game. These extend from the simple *smiles* to detailed actions that take many lines to describe.
It is also advised to try and have a clear idea of each of your character's individual traits, personalities, goals and so on, so that you may keep each character both seperate and played in a consistent manner. Of course a character's personality may and often should change depending on circumstances and events, but drastic, unexpected shifts should be kept to a mininum.
However there are some things you should pay attention to to avoid the wrath of fellow players.
Do not express character thoughts in rp. Even though in books you may see descriptions of thoughts, even if it's not written in first person, Cantr is not a book, and there are different level readers, some of which cannot separate themselves as a player from their characters. Thus even though a player could read about something a character was thinking, the character he or she is playing shouldn't react to this since our characters are not psychics. And after a while of playing you find annoyance in players explaining their choices through character thoughts or meta text because there's no way you can legally reply to it in-game. So please avoid.
Do not rp having items your character doesn't really possess. Now that big weapons and some tools are visible, you cannot fool people into thinking you have for example a sword, but before there was no way of telling if one is telling the truth if they say *waves his sabre in the air* unless they use it for something in a way that's included in the game mechanics. If the person doesn't have such item it's really poor playing.
Do not force actions onto others. (This is sometimes called auto-hitting.) All characters in Cantr are played by real people. There are no NPCs. Thus everyone has their free will and you shouldn't put them in a situation they have to ignore some action you did just because you were being unreasonable.