It's easiest if you understand the coding systems that are used to categorize commodities for which trade data is collected. At any one time there are several systems, and the coding used to report certain statistics from a certain government will change over time as well. Please see the tab on coding systems.
Current data are available electronically, although if you just need a simple aggregate number a paper resource may be as easy to use. Historical data may be available only in paper or microfiche. Be aware on whether you're looking for total country-to-country trade data, data on total imports or exports of a particular commodity into or out of a specific country, or detailed country-to-country data for a specific commodity. Please see the tab on sources for trade data.
If you need to choose a commodity to study for a class assignment, scanning through a list of commodity codes is a good idea to find a cleanly defined product
It's more pragmatic (for the purposes of a class assignment) to choose a product based on the data available for it, rather than get your heart set on a product that doesn't have data.
If you need to study trends over time, remember that it takes some time for a new product to be given its own numerical code and show up in trade data. For a while, it will be lumped in with similar products.
Modern electronic products are difficult to focus on or to follow back many years, especially if the product is built of subcomponents, each of which may be coded separately.
Products that are commonly taxed for political reasons will be broken down into detailed categories in tariff schedules.This includes textile products, alcohol products, and jewelry.
If data is only reported at, say, the 10-digit HS level of detail and not aggregated to fewer number of digits, you many need to aggregate it yourself.