Each country's customs regulations are different however provided prohibited items are not shipped, customs nightmares can be avoided. It's best to check the relevant custom authority "beforehand" to ensure all items being sent comply. Prohibited items may include:

Alcohol,

Antique furniture,

Food, plants, herbs & spices (anything edible or drinkable inclusive of supplements, vitamins, body building formula, teas, medicines).

Any weapon, or items that resemble a weapon.

Firearms, ammunition and explosives

Hazardous items, such as fireworks, toxic or poisonous substances.

Items made from animals on the endangered species list (e.g. ivory)

Unprocessed furs, skins and hunting trophies

Dried flowers, bulbs, seeds, pine cones, etc.

Soil, sand, straw & hay

Used tires,

Pornography

Narcotics

Some countries also prohibit importation of cosmetics, make up, perfumes, and scented erazers.