One thing you must keep in mind at all times when evaluating products to import is consumer safety regulations and other agency requirements. The U.S. especially is notorious for the number of possible compliance agencies (FDA, EPA, DOT, CPSC, FTC, etc.) your products will be expected to comply with and almost all countries have their own agency(ies). Food, drugs, and weapons are their own monsters that I won’t cover. However, aside from those three, most regulations relate to safety. Basically, if you’re product poses any reasonable risk of serious injury it may be subject to certain regulations and standards. If kids are involved, normally under the age of 6, there’s likely some form of requirements (think about those “Beware of children choking on this” labels).
The vast majority of products are not subject to any special requirements. Some are obvious candidates for special requirements, like any nuclear or radioactive items, and others not so obvious, like bed mattresses. You can refer to the US Customs Commercial Importing guide, page 106, for a description of product types subject to special regulations.
The best thing to do is to ask if your product is a food, drug, weapon, poses a reasonable risk for serious injury, or is used by kids? If the answer is yes, research your product more in depth to determine if there are any requirements or give your local customs agency or customs broker a call before you decide to import the item.