Similar to giving a name to a new shop, a good name can play an important part of the success of a business, a domain name that is easy to remember and instantly catches the attention of a person as well as the ability to deliver the message of the product carried by the name across, can help a lot in marketing.
Your registered company name as domain name
If you have a physical shop and planning to extend your business online, obviously you would want to register a domain name that is the same as your shop name, this will give your online customers a sense of confident if they have been shopping at your physical shop.
Choose a keyword domain name for your new online business
If you are starting a complete new online website, then you may want to spend some time thinking of a suitable name that best fit your website theme, easy to remember and brandable. If you can still register a short domain name with keyword to your niche, don't hesitate to jump in ! However, it is not a must to have a domain name with keyword in it, ultimately the website content plays a more important role, and most short keyword domains has already been taken, and long keyword stuffed domain names is not easy to remember and difficult for brand building, a short and easy to remember domain without the main keyword can still be a good choice, do take note that a good name can help a lot in brand building process.
Top-level domain or country level domain ?
Other than the domain name, you may also want to consider if you are targeting audience from a specific country. For example, if you are only selling your product to buyers in your own country, than you might want to consider registering a ccTLD (i.e. co.uk for UK websites). Why would you want to do this ? search engines are serving local results, websites register with country level domain are giving more weight when search engines are serving local search requests. If you are not targeting local audience, then it would be good to register top level domains (i.e. .com,.net,.org etc.).