Show, don't tell. This means allowing the emotions to come from the action, rather than explaining them. For example, rather than writing that "Ben was angry," write how he just threw a chair across the room or punched a wall. Showing is more interesting than telling.
Use dialogue. Angry speech conveys that someone is mad. Romantic words tell the tale of love. Dialogue is a powerful tool for writing different emotions. Try adding emotional richness by using colorful dialogue. You can learn a lot about the relationship between two people by the way they speak to each other and the things they say.
Create well-developed characters. If your readers think they know your characters well, they will better interpret the story's emotional ques. It's like knowing a friend--you begin to anticipate how certain events affect them emotionally. You also care what happens to them, and that increases the emotional content in your book. If your readers don't know the characters well and aren't emotionally invested in them, you will lose a lot of emotional impact.
Trust your readers. If your main character's partner just died, you can depend on your reader to know that she will be sad. Readers don't like to be spoon-fed. It's insulting, and good writers don't do it. If you have written the scene well, your readers don't need to be told how the character is feeling.