There is no universal method for getting information on enterprises and their activities. However you can save yourself valuable time by asking yourself a couple of simple questions. And then by matching your query to the most appropriate resources. This should at least partially answer most queries, and at very least provide a contact within a company for you to make appropriate enquiries personally.
Q.1. In which country is the enterprise located?
Q.2. What kind of information do I want?
If all you want is simple information such as a contact for correspondence or the identities of principal officers, the place to start is the company's website. If you want more detailed information, you'll need to broaden your scope into the online databases, web sites and available print publications listed in the Resources by Region tab.
Information on Irish companies
Researching Irish companies online can be hit-and-miss. You'll get basic information (activities, officers and contacts) either through the company's website or through Fame. If you seek financial information on a PLC, recent annual reports are usually available on the company's website. Figures for private companies are a good deal harder to find and you may have to go directly to the organisation itself. The database Fame has company accounts, ratios, activities, ownership and management for the largest 2.6 million UK and Irish companies and summary information for a further 1 million smaller businesses. For more detailed analysis, you'll need more initiative, checking various sources. In general, you'll be able to find more material on larger PLCs. For private companies or smaller plcs, information will tend to be more sporadic and possibly confined to a high-profile issue involving that organisation. Consider using company information sites, journals databases and the NexisUK news service.
Information on non-Irish companies
Generally speaking there is more, and better-organised information available for companies based in larger markets and for multinationals (especially for parent companies). You'll find DCU Library-subscribed electronic products like Datastream (available from designated PCs in Library and Business School only). There should be plenty of journal articles and company profiles relating to larger companies in Business Source Complete, and business and market news coverage through Nexis UK. The Library also holds some print reference material, and the picture is completed by a range of freely-accessible web sites providing supplementary material, which are all listed under the Resources by Region tab above.