There are typically two angles to consider in a domain name - catchy, creative domains can launch a memorable brand, but including keywords in a domain can make it descriptive at a glance. Ask.com, Booking.com, SalesForce.com, and Weather.com are just a few examples of Alexa Top 1000 keyword-based domains, but creative domains like Google.com and Tumblr.com are obvious examples of custom domains with incredible brand strength.
If your business already exists then you will want to try to incorporate your current branding into your new domain name. This carries your branding efforts over to your website and is a fantastic way to build your credibility as a brand and expand your sales to the internet marketplace.
Highly relevant domain names are focused toward a specific target audience and should also be search engine friendly. Words have implied meanings and associations, which is why you should do your research beforehand to make sure that your domain name communicates the desired message.
Make it memorable. Users should be able to easily remember and connect with your domain name. Since it is a representation or extension of your brand it will have a large impact on the way others perceive your website and organization. You will only be able to make a lasting impression if people actually remember you.