If you've got the job jitters or are feeling burned out, it may be time to lay the groundwork for a new employment search.

"Your instincts are usually right," says David Opton, founder and chief executive officer of ExecuNet, a career-networking organization in Norwalk, Conn. Get started sooner, rather than later, he says. For most professionals, it's likely to be easier to find a new job while you still have one.

Here are five ways to get started:

Raise your career profile through social-networking sites that work through referrals, such as Linkedin.com and Zoominfo.com. Many recruiters these sites as a starting base, says recruiter David Perry, managing partner of Perry-Martel International Inc. in Ottawa. "You've got to do maybe a half hour's worth of work, and you make yourself eminently findable, without exposing yourself."

That's what Mark Kaplan sought to do when anticipating his layoff. A San Francisco Bay Area research scientist in the often-volatile biotech industry, he's worked for three employers in five years, and in January, he began looking for his fourth. He was among employees at Celera Genomics Corp. to receive a pink slip. "There'd been rumors, and they only intensified as time went on," he says. Mr. Kaplan had been using Linkedin.com for a few years, and updated his profile on the site. "It's a way to keep your fingers on the pulse," he says. "The site works well, because you only accept someone as a contact if you trust them. I've used it to find, or, in one case, reconnect, with colleagues at companies I'm interested in working at."

These groups provide another safe harbor for networking. Participating in a business organization with which your company is affiliated won't raise the eyebrows of your colleagues or boss. "It's where they'd normally expect to see you," says Mr. Opton. Consider volunteering to chair a committee. "If you take a leadership role, it's going to create visibility."

But just attending monthly meetings and mingling during the cocktail hour can boost a job search. "You meet people outside your immediate environment, but you're still below the radar," says Mr. Kaplan, who recently found a new job.

3. Network like a headhunter. Mr. Perry teaches candidates a technique that borrows from his recruiting research:

Target 10 or 15 companies you want to work for. Then use Web search engines to identify some of their former employees and their current contact information. Phone them, and ask them about the company, the potential boss and the department you're interested in.

"You'd be surprised what people will tell you," says Mr. Perry, who wrote about the strategy in his book "Guerrilla Marketing for Job Hunters" (Wiley, 2005).

4. Rebuild your network. When you know you're going to need your network in the next few months, start putting it in place now, says Alisa Cohn, president of A & C Associates, an executive-coaching firm in Brookline, Mass. "You need to figure out who is going to be an important contact for you," she says.

Frank Traditi, a career strategist and executive coach in Denver, says having an established network was key when he switched careers about five years ago.

Mr. Traditi had been the international career-services director for a technology-training school in Halifax when he sensed budget constraints would eliminate his job. To prepare for his transition, he says, he contacted people he'd known from his 14 years in sales in the telecommunications industry.

"Most of my work had some coaching aspect to it," he says, "and these people knew who I was." He called them, wrote emails and met with them for lunch or coffee. "They spread the word about what I did. I went back to relationships I'd cultivated over time. And they either became clients or referred me to others," says Mr. Traditi.

5. Do some self-assessment. Think about what you really want to do. Take into account your strengths, weaknesses, likes and dislikes. Ask yourself what you want more and less of, says Ms. Cohn.

Two years into a three-year stint as a litigation associate at a large Boston law firm, Brenda Ulrich says, she felt "burned out."

She started working with Ms. Cohn to better understand her talents and interests. They listed experiences and projects Ms. Ulrich had enjoyed and analyzed them to discover why. She even drew from what she liked about planning her wedding. "I liked coordinating the details, making timelines, handling the budgets, but also the creative aspect -- looking at colors and flowers and patterns," she says.

Next, Ms. Ulrich interviewed family members and friends about what they enjoyed about their work. "Listening to them sparked ideas in me," she says. From there, Ms. Ulrich says, she identified fields to explore, and made lists of people to talk to.

One of those fields was arts management, and her search led her to Volunteer Lawyers for the Arts of Massachusetts, an organization in Boston for which she'd done pro bono work and interned. She now is a part-time assistant director there, administering a program grant. "I've found I really do enjoy practicing law. It wasn't the law I hated, just the place and the setting," she says.