1. Explain it simply
对 (duì) points toward a target: a person or a thing that is affected.
The pattern is 对 + [target] + [adjective / verb phrase], such as 对身体好 or 对……有帮助.
The whole 对-phrase comes before the predicate, never after it.
2. Show examples
喝茶对身体很好。
Hē chá duì shēntǐ hěn hǎo.
Drinking tea is good for the body.
对 + target + adjective
他对老师很好。
Tā duì lǎoshī hěn hǎo.
He is very nice to the teacher.
attitude toward a person
这本书对学汉语有帮助。
Zhè běn shū duì xué Hànyǔ yǒu bāngzhù.
This book helps with learning Chinese.
对……有帮助
3. Share a tip
Keep 对 and its target together right before the predicate. Say 对身体好, never 身体对好 or 好对身体.