Writing emotion effectively can be quite complex, but it is a vital part of writing engaging fiction. To draw the reader into the world of your characters means pulling on their heartstrings and evoking emotion. That is how you become a masterful novelist. There are three simple ways you can show emotion in your characters.

1) The use of body language

2) Naming the emotion

3) Revealing what the character is thinking about

Fiction writers, more often than not, use a combination of all three, and each has their own positives and negatives. 

Revealing an emotion of your characters can be quite hard, simply because, in real life, a person can feel an emotion without there being any outward signs. On the other hand, a person can exhibit certain body language unconsciously. It is also important to note that using subtle gestures can be extremely powerful. A flicker of the eyes, a slight movement of the head or body can speak volumes. Strong emotions such as anger and upset can be revealed in actions that you may barely notice. Knowing your characters inside and out is so important when writing emotion, as a very slight change in behavior towards a situation will ring alarm bells in your reader that the character is affected by the situation. Finally, the use of body language can only show emotion to a certain extent. The character may be laughing or crying but that does not reveal fully what they are truly thinking. 

Do not fall into the trap of describing how every character feels in a scene; there is actually no need. Every aspect of the scene should be portrayed from the POV (point of view) of the character. What does your character observe at that moment? They may not be aware of everyone's emotions or even their own. Have you ever suddenly realized you are shaking in temper or your hands are gripping the car steering wheel very tightly? Sometimes it takes another person to point out your body language, and it is only then you realize the emotions you are experiencing. 

The three ways of showing emotion through body language are
1. What the character observes in themselves
2. What body language the character observes in other characters.
3. What the author reveals from outside the perspective of the character

Is it important that your character is aware that they are displaying a certain emotion? Well, that depends on the reason for showing it. It is the reader's responsibility to sense the emotion of a character. For example, if a character is driving erratically, it may make the scene more interesting if the character is unaware of their behavior until someone screams at them to slow down. This is where you need to be careful, because since everything needs to stem from a character's POV, they may not be paying attention to their body language, but on some level, they have to be aware of how they are feeling. The final point I want to make is the importance of your POV character noticing other characters' expressions, gestures and speech tones since the reader cannot read the mind of the character.