Visiting Mischief Managed wiki, I found this interesting info on how to Roleplay:
➥ One-Line Example:
[10:44] Ellie Stewart looks around as she walks up to the Hogwarts Express spotting her friend. "Hey Emma! How was your summer?"
➥ Semi-Line Example:
[10:47] Ellie Stewart rubs her tummy as she hears the dinner bell chime in the Great Hall. Once arriving, she walks to her house table and sits down leaning forward to grab a roll of of the table. As Ellie sees her fellow housemates, she gives them a short wave. "Hey, how have your classes been so far?"
➥ Para Example:
[10:53] Ellie Stewart walking through the doors of the potions room, she gathers all of her belongings placing them at her feet before pulling out her parchment and quills. She was not ready for classes to begin again! Her head was still in the clouds from having such a wonderful summer. Yet, here she was, back in her robes, in class waiting for the Professor to begin with another boring lecture. Ellie sighs heavily as she rests her elbows on the table and starts to draw little drawings all over her parchment. Her attention was drawn to the door when she heard it pushed open and she spotted her best friend Emma walking into the classroom. "About time you got here!" She said quietly as she grinned at her friend.
Taken from: Roleplay Etiquette, Explanations & RP Rules