I tell people they need a presence on all the top platforms. Facebook, LinkedIn, Twitter, YouTube and Google+, etc.... More if they have time to set them up. These connections will all provide back links and traffic to their website which most businesses already have.
However, using a social media site as a marketing platform is a different matter. This requires some planning, some analysts, a predetermined budget (either money or time) and the understanding of what their USP is (a unique selling proposition) and who their ICD is (Ideal Customer Demographic). On top of this, they should set goals. Goals should be SMART in nature and of one of three types; goals for network development, goals for positive interaction and goals for closed business.
In the beginning, it is easier to setup and achieve network development goals (i.e. grow your following). Having a decent size following will help you with achieving positive interactions (buzz, viral messages spread ...) And be able to close more business. It's much easier to get a response from a marketing message when you send a message to 1000 or 5000 people than it is if you send your message to 124 followers, regardless of whether it's an email, tweet or Facebook post.
If a business wants instance gratification, it should invest in PPC, (pay per click) on Google, Facebook, LinkedIn, YouTube and other sites. This type of marketing will produce more click to your landing page right away. Of course this assumes you have a compelling message, a decent offer and a strong call to action. If not, the clicks on your site may bounce faster than a tennis ball at Wimbledon. Even with pay per click, planning, testing, measuring and adjusting are part of a winning formula.
Ready, Aim, shoot!
For a person with no budget but have time on their hands, need to plan even more! I suggest that they create a schedule and stick to it. They should also invest in some tools that will let them create a message post conveniently (tablets, smart phones, etc....). I also recommend they use aggregation software (like Hoot suite or Tweet Deck) which will allow them to post to multiple platforms simultaneously plus schedule their post on future dates. If they do these three things, they will be able to create a social media campaign on a shoestring budget.