Domain Name places major role in any business. In SEO point of view it helps a lot in getting better Search engine rankings. In readers point of view it creates a brand value in the web world. It's very important to do little market research in choosing the right domain name, because once you have choosen a name then it's permanent.
First you have to do little market research on you competators and analyze top 10 competators brand names and their domain names. Check how they are sustaining in this competative world. Discuss with business professionals who are going to help you in your business regarding the domain name which you would like to choose.
Points should remember while choosing a Domain name :
1. .com is preferrable if you are targeting business over all the world or else choose the respective geographical area domain name for your business
2. Never use hyphens in domain names. you will loose creditability
3. if some one has purchased the domain name which you want, it they are not using it, then try to contact them and buy it from them. There is nothing wrong in speding little more dollars to get a good domain name for succesful business.
4. If possible keep your niche keyword in your domain name, so that you will get better SERPs with less efforts. Ofcourse it's again depends on the business niche you are into.
5. To have a good brand in market go for .com
6. if your target is search engine rankings (not brand) then go for other extensions like .net, .org, .info etc... whatever suits your business