Shop around for the lowest available advance purchase fares for trips to your destinations on a major airline. Check other online reservation sites, airline sites or call your travel agent.
Write this information down.
The pricing information you've gathered is a good guide to using priceline. Look at the prices that you've written down, come to priceline and make a reasonable offer based on this information. We've found that offers of 20-30% below the best available fare have a good chance of being accepted.
Take advantage of any special offers (sign-up for a credit card, for example) that might be offered during purchase. Accepting an offer will add up to $50 in free bonus money to your offer price -- at no additional charge! It's a terrific way to increase the chance your offer for tickets will be accepted.