Renters pay more than they need to if they’re not keyed into the latest ways to snag the best leasing terms.

Shopping for the best rental rates is now similar to looking for an airline fare, says Ron Johnsey of Axiometrics, a Dallas firm that analyzes leasing.

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“When you book a flight online, you can see what the different fares are based on what time of day you leave and how far out you book that flight,” Johnsey says.

Likewise, large companies that rent out hundreds of apartments now typically have websites that allow consumers to fiddle with move-in dates and the lease length on various units, coming up with various price offers.

“Consumers might see rates change as frequently as daily,” says Janine Steiner Jovanovic, president of YieldStar, a Carrollton, Texas, firm providing the computerized systems used by apartment companies.

Whether you’re looking for a rental with a large company that maintains a website or shopping among buildings owned by small landlords, the same principles can lower your monthly rent by up to 10 percent or 15 percent, according to industry executives and observers.

The lease length difference

The 12-month rental lease is the most typical, but there’s no reason it can’t go longer or shorter. An unconventional length can benefit the landlord, who in return can offer incentives for the renter to go either long or short.

On average, “somewhere between 50 (percent) to 70 percent of tenants move out each year,” says Steve Lefkovits, publisher of MultifamilyRevenue.com.

Although there are some parts of the country with their own unique moving seasons, moves in and out tend to occur from May through early September, Lefkovits says.

From a landlord’s viewpoint, it’s often advantageous to have a lease expire during the busy season, when a tenant can be found more easily. Therefore, if you’re starting a lease in March, there may be a rental-discount incentive if you take a 15-month lease ending in the next summer.

When you’re not dealing with a company that maintains a website with pricing differences by lease length, simply tell the landlord or leasing agent that you’re willing to be flexible on the term if it gets you a better rate, says Joseph Greenblatt, certified property manager and president of Sunrise Management Co. in San Diego.

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The move-right-in deals

As if on opposite ends of a seesaw, rental rates have been rising while housing prices seem anchored at bottom. All things real estate-related are local, but on a national basis, residential rents rose 2.3 percent at the end of last year from 2009, according to the New York research firm Reis Inc. Moreover, through 2014, Reis forecasts national rental rises of 2 percent to 3 percent annually.

For landlords, vacancies mean lost revenue. That’s why units that are available now might be had at a lower rate than one that is occupied and will be for a few weeks or months more.

It’s risky to wait until you absolutely need to move to secure an apartment, because there are no guarantees you will find what you want then, Johnsey says. Still, the lease price on a vacant unit that’s been on the market for a while may be lower than a similar unit, he says.

Moreover, the higher the number of vacancies in a building, “the more likely that there will be specials and concessions,” says Mark Moran, vice president of MyNewPlace.com, a rental finder website.

Indeed, Moran adds that while rents have risen nationally, there are markets such as Las Vegas where vacancies abound and discounts and concessions like free parking are offered to fill the oversupply.

The midmonth, midweek advantage

If you were managing a building, would you want your staff overtaxed with many tenants moving in and out on the same day?

Of course not, says Tammy Farley, principal of Rainmaker, an Atlanta firm that develops apartment revenue management systems.

That’s why there may be a slight rate advantage for move-in during the middle of the month, rather than at the busy beginning.

What’s more, calling leasing agents midweek, rather than on busy Mondays and weekends, should allow you more time to talk — and express your willingness to be flexible on lease length and other saving tactics, says Moran.