How exactly should you (what does it mean to) use appropriate eye contact, adequate volume, and clear pronunciation?

To keep eye contact and not to look away like your ignoring them

Eye Contact:

Look at them, and not like you're ignoring them.

Adequate Volume:

Satisfying volume, as in you hear them, and not some other talking, and making sure that you only hear them.

Clear Pronunciation:

Talking clearly, and not all slurred.

Example:

"I luh-ikee you too"