LinkedIn is still the social network most people use for professional purposes. So make sure you set up your account carefully and keep it immaculate. Use it like an online CV.
Firstly, you should understand that LinkedIn is nothing like Facebook! There are no games or photo albums. You can only upload a profile picture (which should be the same one you use for Facebook and Google+), and then all you can do is describe who you are, what job you are doing, your professional experience, information about where you studied and what projects you are involved in.
Unlike Facebook and Google+, many business people, company directors and big decision makers are on LinkedIn, so use it with some regularity. I have made some excellent contacts and started business dealings on LinkedIn.
I suggest you have a look at this video during my Seminar: