Let's say you used to manage a sports shop. Far better to make use of your experience and expertise by dealing in sports goods rather than something you know little about such as fork-lift trucks.
Other important considerations include:
Is the product price competitive compared with other goods in your target market? Ideally your product should be slightly cheaper than the competition once you've accounted for freight, customs duties and other costs.
Does potential demand make trade worthwhile? Is demand year round or seasonal? How long might it remain in demand?
Are there any similar products available in your chosen market?
Safety and Legality
Is the product reliable? Is it covered under warranty? Can it be repaired if necessary? Are there any trade barriers preventing its export/import? Does it conform to national safety standards? Toys from the Far East, for example, are attractive to UK importers because of their low prices, but not all meet EU safety standards.
Is it appropriate for your target market? For example, electrical goods may be wired for the US's 110v supply rather than the UK's 240v supply. Remember practical considerations. For example, foodstuffs may not be suitable unless they have a reasonably long shelf life. Bulky goods will be expensive to transport, so may also be unsuitable.
Above all, try to narrow down your choice of products early on. It makes the search for manufacturers and customers far easier, and it lessens the likelihood of having to drop a product after you've spent time, money and effort developing it and setting up contracts. Taking time to search for the right product is vital.
If it is particularly cheap and/or innovative you can develop a successful small business in a very short time.