You should take some time and try to understand their values and culture. This is needed because, if your values resonate with the media agency with which you will be working, it will become quite easier to make them know what you want and your values associated with your company. And at last, the quality of work would be quite much better.
For any business to have a digital media presence, a website is important. Hence if your media agency that you want to hire does not have a good website, it is hard to say if they hold expertise in the marketing domain. You should always try to hire an agency that has built up their website with all the quality content and details, this proves that they have good experience in delivering the services to clients in domain or media and marketing.