LinkedIn

If Facebook had a professional sister, her name would be LinkedIn. Some 150 million career-oriented users have profiles that tell the world who they are, what they do, and the chronological trail that got them there.

It's today's largest professional social networking website, and you're selling yourself short if you don't have a profile there — especially if you're in search of a new career. LinkedIn is an effective space to network and make contacts.

"If you want a job at Company X, you may not know anyone, but one of your LinkedIn connections may and you can ask for an introduction," says Deb Silverberg, social communications and strategy manager with AARP for money and work issues. "It's a virtual water cooler for people all across industries."

But you've got to know how to put your best foot forward. Think of it this way: Would you wear a pair of sneakers with a business suit? Not likely.

• Do register and create a comprehensive profile to increase your visibility. LinkedIn ranks high on Google searches, so make sure that when people find you, they're impressed by what they see.

• Don't make your profile photo a holiday snapshot with the grandkids. Make it a recent, professional-looking photo of just you.

• Do participate in LinkedIn groups (alumni networks, previous companies you've worked for). It's a great way to reconnect with former colleagues.

• Don't overlook the job search function on LinkedIn. After all, that's what the site is for!

• Do build relationships by being a resource for others first. Pay it forward by using your knowledge and contacts to help someone (without expecting anything in return). Then someone else will help you. You can write recommendations for your coworkers and they can do the same for you.

• Don't request a connection with someone you don't know, even if you think that person can help you get a foot in the door somewhere. "It's considered poor LinkedIn etiquette and can be considered 'spammy,' " Silverberg says.

Next: Learn how to tweet your way to a new job. »