Cashing in Frequent Flier miles is all about the stuff they don’t tell you. Most airline Web sites detail how many miles you need to fly where, and how to earn miles. But actually using them can change the game.

For example, I booked my flight to Auckland on American Airlines. Travelers can have one stop-over per continent on their route, for up to a year. I had three options for New Zealand. I could fly Quantas, which stops in Sydney, Air Pacific, which stops in Fiji, or Air Tahiti Nui. I chose the latter, so I get five days in Tahiti, essentially gratis.

A few years ago I looked into using miles to Europe from Texas, to visit friends in London and Warsaw. I could have listed Warsaw as my final destination, and stopped in London, saving the extra cost of a flight to Warsaw. I could have also stopped in Baltimore on the way over or back to visit my folks. I found a great price on a flight to London, so I saved the miles (and boy am I glad!). But I loved the options.

When booking a trip with miles, American holds the seats for two weeks as a reservation before printing the actual ticket. The reservation can change unlimited times, and every change extends the two weeks. When I initially booked my current trip at the beginning of March, my only options had me leaving near the end of June. I called back the day before the reservation expired, and enough other people had changed their minds that I got the dates I wanted – and I have until March 31 to change again.

I’ve always used American and had great luck. The miles link to my credit card, so as long as I spend at least $1 every two years, my account stays current (trust me, that’s not a problem. A little too much of “not a problem.”)

I had Delta miles once. They expired. An entire domestic flight. I’ll never sign up with them again.

One more stopover note: you can’t book a round-the-world ticket on a standard award. So I couldn’t fly to Auckland via London and Dubai, or some such. You have to pick either an Atlantic or Pacific route, whichever is closest, and return the same way. Trust me, I tried.