The diamond that displays after most choices shows the player how their choice has affected a certain character's level of affection. The color of the diamond corresponds to a certain character. (It is mostly easy to guess based on the characters in the scene).
If the arrow moves away from the diamond, you have improved your relationship with the character. If it moves towards it from further out, then affection has decreased. Some choices do not affect your level of affection at all, and in some (rare) instances, you won't be able to tell which way the arrow is moving.
Now - the arrow gives you a general guideline, but it doesn't tell you everything, namely how significant the choice is in the route. Some choices will increase affection immensely, while others may increase it a small amount (and the same can be said for decreases).
The hints for Clement are that his route most closely aligns with a traditional dating simulator, and also, he favors a person that is hard-working, honest, and also can call him out on his silly attempts at flirting. ;) Good luck!