Why classification matters
The class you pick has a direct effect on whether your trademark application succeeds. If the Trademarks Office rejects your application, it will not return the filing fees you paid. Objections and oppositions are becoming more common, so it's wise to have a trademark expert review your choice and judge how well it holds up against competing marks.
Finding your class number
Marcaria.com offers a Trademark Search Tool that can help you work out the right class number for your products or services.