I'll start with Twitter.  It's very simple.  To be successful on Twitter, you must give people attention.  You want to be retweeted to a huge audience?  Give someone a genuine compliment.

That's it, I just gave you the key to unlocking the universe.  Now if you are still interested, I will explain in more detail.  When I put a tweet out into the atmosphere it will by default fall onto deaf ears.  If you want someone to listen to you, you have to listen to them first.  If you reply to someone's tweet, you just earned your first follower.  They are flattered and they will show their appreciation with social currency.  If they are flattered, they will retweet you to their 50,000 followers.  Now you have influence AND followers.  You have credit that can be spent in any way you want but there's only one store that takes your money:  Twitter.

Here's proof:

If you're keeping track at home, that's over 60,000 people in 3 retweets that know who I am because I paid someone some well deserved attention.

Now that you are armed with the most powerful weapon in the twitterverse, go out there and make some new friends. Let the people whose products you rely on know how much you love their stuff.  Share someone's tumblr account to your followers, link to your favorite song.  You are the one who runs social media, make it count.