ooh, ugh, eew

Ooh or ooh is an expression of delight or surprise--
Ooh! What a pretty cake!
Ooh, look at that beautiful car!

Ugh or ugh, also eww ( rhymes with ooh ) is an expression of disgust--
Ugh! Who left this mess?
Ugh, that smells nasty!
Eww, that's disgusting!

Now that you know that, you can say--
"Ooh, that guy is cute!"
"Ugh, he is not cute, he's a creep."