Here’s how you might fill out the sentences with "should" or "shouldn't" regarding Tet holiday customs:

1. One **should** visit relatives and friends.
2. One **should** sweep the house on the first day of the new year.
3. One **should** give good luck wishes to others.
4. One **should** give children and the elderly lucky money.
5. One **shouldn't** say bad words or do bad things.
6. One **shouldn't** break glassware.
7. One **should** buy and wear new clothes.
8. One **shouldn't** wear black or white clothes.
9. One **shouldn't** eat squids, duck meat or shrimps.
10. One **should** offer visitors something sweet such as biscuits, sweets or nuts.