There are a few items that we come across, or get asked about often. Some of them are allowed, some are not, and some require you to get a permit before bringing them in. Even if an item is allowed, there might be some caveats. Here are some of the common ones:
Apples, mandarins, oranges, and other fresh fruit, etc.
Alcohol, tobacco and general goods.
You can bring in medicines for personal use, but there are restrictions.
Meals, cakes or anything you made yourself can generally not come.