Many companies are now using social media to marketing sites such as Facebook and Twitter for their business. There is a number of popular social media sites that you can use and some will work better than others for you, depending on how much time you have to update them and what you are trying to sell. Facebook is often the first one that businesses use as it is fairly easy to set up and you can quickly build up a decent following on there.
You need to make sure that you set up the right sort of profile on Facebook as this can restrict what you can do. If you want a profile which can also have discussions on and other members share ideas etc then you may want to set up a group page. If you want a page that only you can add content to and people can like then you may need to set up a page instead. You will need to have at least one private profile that is linked to the page and can be admin.
If you have a business that deals direct with the public then social media is especially important as you can connect with individual users on a personal basis. For example if you own a dog grooming business, then Facebook can work well as you ca join local groups and ask people to follow you. Although business to business companies may find social media a little harder, social media profiles can help establish and build a brand.
The beauty of social media, is that much of it is free, it just takes time which some businesses simply do not have.