Register the Domain Name in All Three Main Top-Level Domains
Registering the domain name in all three main top-level domains (and any other top-level domains which may provide value) which all direct Internet users to the same website is a relatively inexpensive way to ensure that a variation of the domain name is not used to re-direct customers to another company's website.
Register Common Misspellings of the Domain Name
Registering common misspellings of the domain name will help reduce the risk that an Internet user will misspell the domain name and be directed to another business's website.
Obtain a Federal Trademark Registration for the Domain Name
If a domain name acts to identify the source of products or services (and not merely as an indication of the address of a particular website), it may be possible to register the domain name as a trademark with the United States Patent and Trademark Office. Though federal law protects both registered and unregistered trademarks, the owner of a properly registered mark is afforded additional benefits not available to owners of unregistered marks.