Finding a good domain name that isn't already in use, can be a nightmare. Established offline businesses might find it particularly hard to find a name relevant to their company name unless it's very unique.
So what do you do when your perfect domain is already in use? You find a way to add to the domain name and still make it relevant. For example; if you own Dave's Dinner on the beach in California, you may find davesdinner.com has already been taken. Try to add to the domain until you come up with something fitting...like DavesDinnerOnTheBeach.com or maybe DavesDinnerCali.com
