Hi - it depends what you are importing. Some products (footwear for some countries for example) have quotas, other restricted and potentially harmful products need licenses.
There is an import_export guide you can download from this page: Link hidden: Login to view
That should answer a few questions but when you come to import a particular item you'll need to use a customs broker. They'll be able to tell you what forms you need for the import and help you with all the technical details :)