FORTUNE — It’s beginning to look a little more like Christmas for jobseekers. Toys R Us will add about 45,000 salespeople, toy demonstrators, and warehouse workers for the holiday season, the company announced a few days ago. Macy’s (M) plans to bring on 78,000 people for the holidays, a 4% increase over last year’s holiday hiring. Altogether, predicts Chicago outplacement giant Challenger Gray & Christmas, seasonal payrolls will swell by about 620,000 over the next three months.

That doesn’t mean all retailers are bringing more hands on deck. Discount Shoe Warehouse (DSW), for instance, saw double-digit sales gains in the quarter ended July 31, but is nevertheless stepping cautiously. Rather than add seasonal workers, the company plans to ask its existing employees to put in more hours.

With such a mixed outlook, applicants are starting their job hunts earlier than usual, says a new poll from hourly-worker job site Snagajob: Almost half (45%) of those hoping for a holiday gig began looking in August and September, while one-third (33%) said they’ll start in October.

Applicants off to a late start face stiffer competition this year from those who have held holiday jobs in the past, notes Snagajob CEO Shawn Boyer. The roughly 1,000 managers in the survey said that 53% of their temporary hires “will be people who worked for them in past holiday seasons and are coming back,” says Boyer. “That’s an eight-point increase over last year.”

Even so, casting a wide enough net can boost anyone’s chances of landing a seasonal gig.

“Keep in mind that all kinds of businesses, not just retailers, need extra help during the holidays. So try catering companies, restaurants, theatres, delivery services like UPS,” Boyer suggests. “Don’t forget to ask around among friends and family members.”

Persistence often pays off. “There is constant churn in the retail industry, which has one of the highest turnover rates of any business,” says John Challenger, CEO of Challenger Gray. “You may walk into a store one day and they’re not hiring. Walk in the next day, and someone has quit.”

How likely is a holiday job to turn into a permanent position? Toys R Us, which recruits many of its employees through Snagajob, says that about 10% of its seasonal hires stay on past January 1.

“Ten to 15% is about the average for all seasonal employers,” says Shawn Boyer. “If you want to be one of them, start by mentioning that in your first interview. If the company is aware that you’re looking at this for the long term, it gives them a chance to evaluate you somewhat differently than they would someone who will be gone in a few weeks. They’ll be watching, in part, to see how good a ‘fit’ you are with their permanent team.”

With that in mind, treat your seasonal job “like an audition,” he says. “Get there early, stay late, be enthusiastic, and volunteer for duties nobody else wants and hours nobody else likes. As the newest person, you’ll probably be asked to work nights and weekends anyway, so put your hand up for those unpopular shifts.”

One encouraging note:  While the competition for permanent jobs is ferocious everywhere these days, not everyone who takes a holiday gig wants to stay on past New Year’s.

“Some people are only there to make extra money to spend on holiday gifts, and they will apply only to places where they want to shop, so they qualify for those great employee discounts,” Boyer says. “Lots of the seasonal workers at Toys R Us, for example, are parents who aren’t interested in working there in 2012. They just want to be great Santas.”