Keep a close eye on your child, don't let him run around.
Tips
mistakes
The reading most learners meet first is kànhǎo, to be optimistic about something. Here 看 means to guard, the same reading as in 看守, so the phrase is an instruction to watch something closely, not a verdict on its prospects.
usage
Nearly always a request or an order: 看好 your child, your bag, your seat. The 好 is a result complement carrying 'and do not lose it', which is why the phrase sounds like a warning.
