How do you know if people are joking around or if they are serious?

Answer 1

If you know them well enough you should be able to tell from their body language or facial expressions. Some people may laugh or twitch when they are pretending to be serious others may not be so obvious. In this case confront them and ask them. If you can't do that then think logically about what they said. Think of what happened that day or recently or about what was on the news. Try and work out in your head if it's a joke or serious.

EDIT: The above answer is right BUT it is ultimately more important whether you want it to be serious or to be a joke. If people are being serious(or you don't know for sure) in a way that makes you uncomfortable pretend you think they are joking and say dismissively humorous things. Sometimes that will make them stop, go away, or switch to pretending they were joking altogether.

Answer 2

You can often tell if people are joking around by their tone of voice, facial expressions, and body language. If someone is serious, they are likely to have a more straightforward and sincere demeanor. Additionally, considering the context of the conversation can also help determine if someone is joking or being serious.