You cannot have social media goals. It's like having copy machine goals. The copy machine is a business tool, and if you need it, it's there to help you meet one of your business goals. Treat social media the same way.
The best way to understand which tools will help meet which goals is to cut through the crap that the buzz is built on. Figure out who is really using social media to meet their goals, and how they are doing it.
Lie #1: LinkedIn is for networking.
Networking should be at the forefront of every entrepreneur's mind. Research from the Darden School of Business shows that startups are most likely to succeed when the founder is great at networking. But LinkedIn isn't going to help you on that front.
LinkedIn is for displaying your network, not building it. For example, you can go on LinkedIn and find out that I'm really well connected. But most of you already know I'm well connected -- I'm a print journalist, blogger, and startup founder, which are all very network-intensive jobs. Which means I didn't build my network via LinkedIn networking tools. I built it offline.
Networks are built on relationships, which grow from conversation. LinkedIn is not for conversations. So you need to go somewhere else to build your network, and then when it's big, display it on LinkedIn so you'll look great.
Lie #2: Twitter is for conversation.
Twitter is an index of people with whom you might want to talk. It's a great index -- you can search by topic to find out who is interested in what, and then talk to them about mutually interesting topics. It used to be that you'd have to suffer through endlessly boring events at conferences striking up conversation to find the people to talk to later. Twitter makes that conference drudgery superfluous; you can talk to anyone you want, by topic or specialty, super fast.
The problem with using Twitter for conversation is that you're going to need way more than 140 characters to make a genuine connection. So Twitter is great for finding people who have similar ideas, and for keeping track of them in a high-level way.
But you still need to go elsewhere -- offline or online -- to solidify the relationship to the point where you would actually care about each other in the way a solid network connection does, but Twitter is a good start.
Lie #3: Blogs are personal journals.
A personal blog is a record of what you're thinking, and that record will represent you online, as a high-ranking search result when someone googles you or your company. So stop using your blog as a diary.
Use a blog as an intellectual exercise to force you into thinking in a disciplined way about things that interest you (or your company). The blogosphere is a cocktail party for the intelligentsia. Make sure you are a part of that so that you can help shape ideas as they grow. There's no better tool for PR than wielding influence as a blogger.
Lie #4: With social media you can get people to do [fill in the blank]
Social media is about being nice. The people who are best at meeting their goals through social media are the most generous as well. When you use social media, give way more than you get. And remember that giving something that requires someone to do something for you (Download my book! Test out my free software!) is not giving. Ask people how you can help them. Read enough about someone to understand what they need and then surprise them. Be interesting without expecting anything in return. You could think of social media as its own economy: Interestingness is the currency; kindness is the way that currency is transported.