The domain should be easy to recall, preferably only characters and .com unless you are looking at country specific audience. There are exceptions to this rule but usually its found that a domain without dashes, numbers, etc are better and easier to remember. you dont want to have say best-domain-name123 .co .in but any day bestdomainname . com is easier to remember and recall. And if you have a good marketing setup then I guess any domain is easy to market and I have seen recently that there are so many new companies with hard to remember names but as they keep marketing over a period of time, you get used to the name!