Formal:
* 好聰明 (hóu cīng ming) - This is the most common and literal translation of "very smart".
* 好叻 (hóu laak) - This is a more colloquial way to say "very good" or "very capable", and can be used to express someone's intelligence.
* 好醒目 (hóu seng muk) - This translates to "very sharp" or "very quick-witted", and implies a high level of intelligence and understanding.
Informal:
* 好鬼醒 (hóu gwai seng) - This is a more casual and playful way to say "very smart" or "very clever".
* 好勁 (hóu ging) - This translates to "very strong" or "very powerful", but can also be used to express admiration for someone's intelligence.
Specific Examples:
* 佢好聰明，考試一定會考得好。(keui hóu cīng ming, hóu si3 yat1 ding6 wai6 hóu si3.) - "He's very smart, he'll definitely do well on the exam."
* 佢好叻，做嘢好快。(keui hóu laak, zou2 je5 hóu faai3.) - "He's very capable, he works very quickly."
* 呢個小朋友好醒目，識好多嘢。(ni1 go3 siu2 hai4 tin4 hóu seng muk, sik1 hóu do1 je5.) - "This kid is very smart, he knows a lot of things."
* 你真係好鬼醒，估到我諗乜。(nei5 zan1 si1 hóu gwai2 seng, gu2 dou3 ngo5 lam5 mat1.) - "You're really smart, you guessed what I was thinking."
Remember, the best way to choose the right phrase is to consider the context and your relationship with the person you are talking to.