I've noticed people are more likely to use a facial expression emoji that they think is likely to be familiar.  Some examples:

Happy (smiley)
Sad (frown)
Angry (anger face)

People who use "love" or "heart" (which is always different each time) are usually interested in relationships, but also as the context reveals:

Happy (girl-with-boy, girl-with-girl, boy-with-boy, girl-with-gay)

Laughing and giggling often indicate pleasure.  It's good to make fun of someone, especially yourself!
assitant
Can you tell me about that?
assistant
How do you know what emojis mean?
user
I keep track of trends in language use.
assistant
Sometimes you can't tell.
user