I created my LinkedIn account in late high school for the purpose of determining whether my ex-boyfriend's new job was legal or not. At the time, I didn't know that every person whose profile I viewed would receive a message letting them know they were being watched. Perhaps the only real LinkedIn tip I can give you is to remember not to creep on other people's profiles for non-career-related purposes—they may find out about it.
Selecting your LinkedIn profile picture is perhaps the most important part of the process. Good-looking people are often assumed to be competent and likable, so if your photo is good enough, a future employer might overlook the rest of your shortcomings. If you're currently in an "awkward phase" that began in late elementary school and has no foreseeable end in sight, choose a photo from the last time you were cute. Nothing says "high-energy go-getter" like a picture of yourself as a two-year-old smearing cake all over the dog.
The "skills" section can be scary if you're like me and most of your work experience can be described as "unskilled labor." Right now, my LinkedIn profile just lists "self-deprecation," and no one has even endorsed me yet. Luckily, most of the skills on LinkedIn are fairly vague. If you list "project management," no one will guess that the project in question was for the third grade science fair, and that your poor management skills are the reason your classmates are still not speaking to you. "Communication" is another easy one to add. If you're successfully reading this article, then we're communicating right now. Connect with me on LinkedIn and I'll endorse you.
Don't be afraid to express yourself on your profile—employers want to get to know the real you to see if you'd fit in with their corporate culture. Treat your "self-summary" the same way you treated the "about me" section on your Myspace in 2007. Copy-paste your favorite song lyrics, a few inspirational quotes from authors you've never read (courtesy of BrainyQuotes.com), and a shout-out to your best friend. Hiring managers will be able to tell that you're friendly, approachable, and have no time for haters&drama.
Look for connections everywhere. Did you get someone a drink at a party? They can endorse you for "bartending." Did you say "thank you" to your cashier? Add him as a connection, so he can endorse you for "basic manners." Write your full name in sharpie in a truck stop bathroom and soon you'll have plenty of connections willing to endorse you as a "good time." Have a good time on LinkedIn and, when all else fails, add random people who share your first name—you probably have a lot in common.