Lots of people I know don't understand my enthusiasm for credit-card sign-up incentives.

Maybe this will help explain why I'm such a big fan: My family just returned from an eight-night vacation in New Mexico, and we spent less than $500 on airfare and hotels for all three of us.

Incentives for signing up for credit cards can include large amounts of frequent-flier miles and hotel points or free hotel nights. After a year or so of taking advantage of such offers, we claimed airline tickets, hotel stays and other incentives worth more than $3,000.

That's some serious savings, and for me, it was well-worth the time and effort needed to make the most of those deals.

Some of the frequent-flier miles and hotel points that I used for the vacation came from charging purchases on hotel- and airline-affiliated credit cards, and through a variety of small promotional offers. But most of them came from sign-up incentives.

I'll break down the details, but first, two important notes: Many credit cards offer great incentives for signing up, but they aren't worth pursuing if you're going to wind up paying interest on new credit-card debt. Avoid interest charges by paying off balances in full, on time, every time.

Also, opening and closing lots of credit-card accounts can hurt your credit score. I haven't seen my score harmed by opening or closing a few accounts a year (I subscribe to a credit-monitoring service and I do keep track), but I know the risk exists if you get carried away.

Now, here's the New Mexico vacation savings breakdown:

--Three round-trip tickets from Charleston, worth $1,965: Acquired with 25,000 US Airways frequent-flier miles and 50,000 Delta miles, most of which came from credit-card sign-up incentives.

--Two nights, Hyatt Regency Tamaya Resort & Spa, worth about $700: Acquired by signing up for a Hyatt Visa card ($75 fee), which offered two nights at any Hyatt, any time, as an incentive.

--Two nights, Sheraton Albuquerque Uptown, worth $325: Acquired with 8,000 Starwood hotel points, mostly from using a Starwood American Express card (10,000 points for signing up, 1 point for every $1 charged).

--No checked-baggage airline fees, saving $100: Our checked bags flew on Delta, exempt from baggage fees as a benefit of having a Delta Gold American Express card.

Add it all up, and our savings were huge. And that's why I'm enthusiastic about credit-card incentives.

No need to fly frequently

When I tell people my vacation flights were free with frequent-flier miles, they often respond that they don't fly very often, so they don't bother with frequent-flier programs.

I don't fly often, either. I get most of my miles from credit-card offers, using airline-affiliated cards, and taking advantage of airline promotions.

It's nice that you can (typically) get one frequent-flier mile for every dollar you spend using an airline-affiliated credit card, but it's the 20,000 or 30,000 miles you can get for signing up for the card that gets you a plane ticket.

Switching can pay

If one credit-card offers 25,000 frequent-flier miles to sign up, and no fee for the first year, that's great. But why then pay a fee to remain a customer in the second year?

The benefits had better be good, because as long as you have good credit, there will always be a rival card offering an attractive sign-up incentive.

I have found that some cards offer ongoing benefits far more valuable than the annual fees charged. Other cards, I've canceled before the annual fee comes due.

Betting their money

This was an unusual deal I couldn't resist while on vacation: free casino gambling.

The Sandia Casino in Albuquerque, N.M., was offering $60 to gamble with as an incentive to visit (you had to sign up for their free Players Club and provide an email address).

The casino credit had to be wagered on slot machines and table games, but once the $60 had been bet, what remained was the player's to keep.

I got to have some fun and was lucky enough to eventually leave with some of the casino's money.