You should look for a design company that is easy to work with
. This means they should have someone available for you to recommend changes in the design if you find it not suitable. Apart form just having a good portfolio the company should also have a record that proves they have delivered what they say. Similar to other online marketing, website design is also somewhat result based. So, it means that you will just not want to pay the company for what they have designed but will also want to ensure the work is correctly put forward or is SEO friendly so that it helps you promote your business online.