For emphasis:
* "I know exactly what you mean."
* "He said exactly the same thing yesterday."
* "This is exactly what I was looking for."
For precision:
* "There are exactly ten people in the room."
* "The recipe calls for exactly two tablespoons of sugar."
* "I arrived at exactly 5:00 PM."
For agreement:
* "You're exactly right!"
* "I feel exactly the same way."
* "That's exactly what I wanted to say."
For clarification:
* "What do you mean exactly?"
* "Could you please explain that exactly?"
* "I'm not sure I understand exactly what you're asking."
To show contrast:
* "It wasn't exactly what I expected."
* "She didn't exactly jump for joy when she heard the news."
* "He didn't exactly apologize for his behavior."
The best way to use "exactly" depends on the specific context of your sentence.