HTSUS (Harmonized Tariff Schedule of the United States) classifications can be straightforward or not, as these two examples illustrate:
8532.10.0000 Fixed capacitors designed for use in 50/60 Hz circuits and having a reactive power handling capacity of not less than 0.5 kvar (power capacitors).
A thorough classification includes HTS lookup, GRI (General Rules of Interpretation) review, checking notes, and searching CROSS (Customs Rulings Online Search System). This is the procedural aspect of classification, but there is more. Most commodities require interpretation of the tariff language based on experience. Finally, the process needs to be documented for future reference and parts lists updated.
I sometimes recommend a binding ruling to ensure accuracy in entries. Binding rulings provide uniformity across all ports of entry, and protect the importer from variations in interpretation from current and future CBP personnel. Rulings can be requested on valuation and country of origin as well as classification. The downside to obtaining a ruling is that you must follow it or be subject to penalties, although rulings can be appealed.
If you decide to obtain a ruling it is best to engage an expert to draft your request for a specific classification rather than leave it totally in the hands of CBP.
For help with binding rulings contact email@example.com.