Want to fly cheap? Time to break some bad habits.

Like buying the first cheap ticket you see or waiting until the last minute to book a fare.

As the economic slump continues and both business and leisure travel declines, fares are getting cheaper as airlines try to fill seats. A roundtrip ticket between San Francisco and Boston for instance, was selling on Feb. 4 for $238, down from $400 on Nov. 1. Even with such bargains, however, travelers need to know a few tricks to get the very best prices.

First, don't hurry.

Matthew D. Weyer sometimes spends hours researching fares online. Knowing what a ticket usually sells for allows him to spot cheap fares almost immediately.

Weyer sets up e-mail alerts for prices on the route he's shopping for at fare-watching sites like Kayak.com or Farecast.com. He finds out if discount carrier Southwest Airlines Co. flies a route. He also checks the ticket on booking sites like Travelocity or Orbitz.

Weyer recently shopped for a flight from Greenville, N.C., to Chicago, a ticket he said commonly runs around $410 round-trip. He was tempted at $280. He eventually paid $180 on ...