In July, travel-points expert Brian Kelly posted a surprising announcement on his website, the Points Guy (thepointsguy.com). United Airlines was running a business-class-fare special from New York to Hong Kong for just four frequent flier miles and $43 each way. Sounds unbelievable, right?

Kelly was certain the fare was a mistake, what travel experts call an "error fare," but he told his thousands of readers and Twitter followers about the deal. Many booked the flight before United noticed the error. The airline refused to honor most tickets, but travelers who left for Hong Kong within five days of booking got the round-trip flight — normally about $10,000 — for a few points and less than $100.

"That fare was really unique," Kelly says. "The mistakes usually happen with paid tickets, when an airline will forget to add taxes or an extra digit to the price," Kelly says, adding that it's unusual to have a mistake apply to all flights on one route.

The thrill of error fares and amazing deals is an added incentive for people to rack up miles and book trips strategically. Kelly says that more than ever, credit-card travel-rewards clubs are trying to attract new customers with sweet bonuses.

We talked with Kelly to learn his tips and tricks for racking up 125,000 miles a year (without flying!). Trust us, even experienced travelers will be impressed by how experts get the most out of their bonus points.

How to get miles

Get in on the credit card game: If you want to rack up miles quickly, you have to be in on the credit card game. "It's so lucrative for the companies," Kelly says. "The credit card companies were shedding customers during the recession. Now that economy is getting better, they're looking to get back creditworthy consumers." But Kelly doesn't recommend that people in debt get into the game. It's only for people who pay off balances every month.

How many accounts should you open: It's free to open up miles and points accounts with airlines and hotels, and Kelly recommends opening all of them. As for credit cards, Kelly thinks you can open more than you'd expect:

"You're told it will destroy credit. It's not true. If you have a good credit score, there are people like myself who push it to limits. I got four credit cards two weeks ago and eight last year. If you're not running balances, opening cards will not have a negative impact." But again, you need to keep track of your spending.

Transferable-point credit cards: Not all points are equal. A 30,000-point reward ticket might be 100,000 points at a different airline. That's why Kelly recommends a transferable-point credit card that allows you to rack up points in a central location and use them anywhere. Also, a central pool of points gives you flexibility, particularly if you're getting rewards tickets for multiple people. Kelly recommends Chase Ultimate Rewards and the American Express Membership Rewards cards.

Know your cards: Kelly knows people who keep Post-it Notes on their cards so they know which one to use when spending on travel, gas, dining, etc. "Many categories give you double or triple miles on certain categories," Kelly says. "It pays to keep up with them."

Grab these cards: If you have excellent credit and are in need of a vacation, what's your excuse for not applying for a credit card that gives you 50,000 bonus points, enough for a free round-trip coach ticket to Europe? (British Airways Visa — read the fine print and sign up.) Kelly says StarAlliance points, which share miles among 27 carriers, are valuable, and so are British Airways points, which are interchangeable with American Airlines points. Look for these cards.

How to spend them

Splurge on business class: Kelly is 6 feet, 7 inches tall and likes to fly business class. But there's a mathematical reason to splurge on business class with points: A first- or business-class ticket can cost in dollars 10 times as much as an economy ticket. But when you pay in miles, you're not going to pay 10 times the points for the upgrade. Often, it's only double points to fly business class, and many airlines allow you to upgrade your seat with points. "Business-class awards are generally for everyday people who want an aspirational type of award," Kelly says. But if you're getting miles easily, you may as well splurge on something that's usually unattainable.

Buy miles: Some airlines let you buy miles and will give bonuses of up to 100 percent when you purchase them. Sometimes it's cheaper to buy miles than a ticket, so check the bonuses before booking.

Shop online through mileage malls: If you're buying an item from Target, did you know you can go to its website through a mileage mall and earn double or triple points just for using that online portal? "It's a no-brainer really," Kelly says. "A mileage mall takes you to the website you're looking for, but you get extra miles for shopping through them, plus the miles from using a mileage-earning card. . . . You're double-dipping. Apple once offered 10 points per dollar through Chase Ultimate Rewards Shopping. Never just shop through a store's website." Kelly recommends Evreward (www.EVReward.com); also check out his site's Beginner's Guide, which lists online portals.

Track them: When you have, say, 10 credit cards attached to mileage programs, you need a mileage manager. Kelly uses Award Wallet (awardwallet.com), a free service that tracks mileage balances and alerts you if miles are expiring. Using Miles (usingmiles.com) and Trip It (tripit.com) are similar.

Jump on it: You cannot spend days pondering deals. "They never last forever, and as exciting and scary as it is to plan a trip to Asia in 20 minutes, the best deals are only offered for a very limited time," Kelly says. "So, think outside the box."

Read the Web: Use social networks to your advantage. Kelly posts error fares or great bonuses regularly, so follow him on Facebook and Twitter and read the comments and community posts on Flyer Talk (www.flyertalk.com). Expert travelers share information and will alert you to a great deal.

Bottom Line

Fall mileage sales and credit cards' initial bonuses can help you rack up miles quickly. Once you have them, book off-season flights with flexible schedules to ensure good fares. Follow experts like the Points Guy and look for sales. A mile is a terrible thing to waste.