If used correctly, social media ca have an extremely positive impact on your business and brand. It allows you access to millions of people, some of which you may not have been able to engage with. There are a number of different social media sites that you can use as part of your marketing strategy, but which ones or how may you should use depends a lot on your time and the type of business you are in.
If one of your employees is going to be managing the social media accounts then you need to ensure that they understand fully what you want to use the sites for such as showcasing previous work or allowing your customers another method of contact etc. They should also know how often they need to post information and how much to post on there. Some companies give a snippet of information on their social media sites but then link to full articles on their website in order to increase traffic.
It may be that you outsource the management of the social media marketing, this may allow you the expertise of someone that knows how these sites work and how best to share information but it will also mean you having to trust someone else with the task of connecting with your customers.