Reader WR asked for “[w]ays to maximize miles *without* use of credit cards.”

I’ll take the question to mean, what are the best ways to earn miles without signing up for credit cards, or using credit cards as the means of earning miles (through bonus categories, or heavy spend – manufactured or not). I’ll allow that credit cards can be used as a payment mechanism for activities you’d do otherwise.

There have been plenty of great opportunities over time. I’ll never forget earning 20,000 Delta miles for a Bosley hair restoration consultation (I had more hair back then). I used to benefit mightily from United’s GroceryMiles program with Safeway. And then there was dumpster diving.

But there are lots of ways to earn miles today:

• Mileage shopping portals

  Sometimes the mileage amounts are fairly small, if you’re only spending $20 and you’re earning 3 miles per dollar that’s 60 miles.

  But you’re earning miles for things you’re going to buy anyway, just start your online shopping at a mileage portal and click to the store of your choice instead of going to that online e-tailer directly. Most online stores give miles or other rebates for your shopping if you do this.

  And the rewards can actually wind up quite large, 20 miles per dollar and I’ve even earned 100 miles per dollar on certain purchases without a promotion to stack – and promotions do abound all the time, especially around the holidays, back to school, and other peak shopping seasons.

  Remember those miles are in addition to what you earn for putting the purchases on your mileage-earning credit card.

  Here’s how to choose which mileage portal to use for your shopping, and here’s my interview with the President of Cartera Commerce which runs many of the sites.

• Buying items through mileage portals, and selling the items

  This is just a variation on the above, an arbitrage play, if you find items you can sell for about what you paid for them you can pocket the miles or other rebates. There are some big players in this space, I’ve written about it in the past, and it’s not something to enter in without being sure you can get your cash out. But there are folks earning hundreds of thousands of miles a year this way.

  The idea is that you can find items that you’ll be able to sell for as much as you pay for them (including transaction costs), and you pocket the miles as profit.

• Actually flying

  Flying 100,000 miles a year on American Airlines, I earn 200,000 miles (without promotions) because it’s not just the one mile per mile flown but also a 100% bonus (based on my elite status) on top of that.

  That’s enough miles for 2 business class roundtrips to Europe or South America, and nearly enough (110,000 miles each) for 2 business class roundtrips to Southeast Asia.

• Opening investment accounts (Fidelity, sharebuilder)

  I used to use Sharebuilder for opening account bonuses, the big miles all came from Fidelity. Like 50,000 miles for a $100,000 deposit.

  Plenty of folks have earned more than one bonus from Fidelity.

  You used to be able to game Fidelity’s deposit requirements but they’ve since closed that loophole.

• Bankdirect checking

  I’ve used Bankdirect as my primary checking account since July 2003. They give me 100 miles for each $1000 of average balance each and every month, and there are signup bonuses as well.

  In a low interest rate environment this is a pretty good return, especially since there’s no tax reporting on the miles but you’d pay tax on interest earned (such as it is these days, on a checking account).

  They now cap mileage-earning based on a $50,000 balance, but that’s still 5000 miles per month if you max out (at a monthly fee for the checking account of $12).

• Miles for Satellite TV

  Signing up for DirecTV can be used to earn 25,000 or 30,000 miles at a time — and with a little bit of effort service can be cancelled and re-upped. If you’re going to have TV anyway, you might as well get lots of miles for it.

These are just a handful of ways to earn miles. It doesn’t account for car rentals, hotel promotions, real estate transactions, insurance, phone cards and plans, survey programs, and even dining for miles.