Clarify exactly what emotion you want to express. Is the character just afraid, or is he terrified? Does he feel embarrassed or ashamed? Identify the level of emotion in your character and be clear about exactly how you want him to feel.
Describe how the character looks, acts and reacts during this emotional scene. Avoid saying exactly what the character feels. For example, instead of saying "Jenny was terrified," describe what she does when she feels terrified: "Jenny's hands began to shake and her knees wobbled." By describing a character's action, you can indicate how she feels without telling the reader. Since emotions are felt differently by different people, using descriptions can help the reader to really understand the character's feelings.
Watch for cliches. Even when you use descriptions to convey emotion, you can fall into too familiar or cliched descriptions; for example, phrases such as "I had butterflies in my stomach" to represent fear or "I was weak in the knees" to represent a crush. Avoid language that is too familiar or stereotyped to be effective.