You need first to research and brainstorm a bunch of creative names. Then, go for a Google search to see if the names have already been used. Decide this will eliminate 50% of your choices.
Choose an easy-to-spell name. Make it interesting so that it can easily grab a client's attention.
Avoid choosing absurd and complicated names that clients think complicated to pronounced and don’t get the idea what it means (give significant thought to names like "Google," "Yahoo," and similar).
Follow trademarks and trade name suggestions and select a particular name associated to trade. After then, be sure you can still get the domain name.