If you have your own brand for setting up the brand for your business then I would suggest you, choose your brand name as the domain name. it helps to increase brand awareness in market.
if you don't have any brand name then you can do keyword research based on the product/service you are offering. then choose the keyword as domain name. but here make sure, it is easy to remember, short , not included numbers and most important it represents or is related to your business.