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You can earn frequent flyer miles without boarding a plane every month and even without leaving house at all. The bottom line to mile earning is to spend, but in a smart way. There are two options to consider when choosing a credit card for earning miles - general travel rewards credit cards or airline co-branded credit cards. On the one hand, earning strategy with both types of cards looks similar as these cards usually come with sign-up bonuses and rewards miles for different types of purchases. On the other hand, airlines' cards redemption options can be more restrictive - you can redeem miles only for specific airline and its partners (if it has any). General travel card miles give you more flexibility - they can be redeemed with any airlines, hotel, cruise or another travel provider.

1.Take advantage of sign-up offers

Many travel cards offer sign-up bonuses. In most cases you will need to spend a certain amount for the given period of time. Taking advantage of these bonus offers is one of the easiest ways to get "free" flights. Make big purchases during the first period of using to qualify for a bonus. Depending on the card, earned number of miles may be enough for a ticket.

General travel rewards card, the Discover it® Miles, has a unique sign-up offer. Discover will match all the miles you've earned at the end of your first year (if you are a new cardmember). For example, if you earn 35,000 miles, you get 70,000 miles. That's $700 towards travel! Your bonus fully depends on your spending - there are no requirements or limitations. You can redeem your miles as a statement credit towards travel purchases - airline flights, hotel stays, car rentals and more. There are no blackout dates.

American Airlines credit card, the Citi® / AAdvantage® Executive World Elite Mastercard® (Citi is a Credit-Land.com advertising partner), offers the following sign-up bonus: Earn 50,000 American Airlines AAdvantage® bonus miles after spending $5,000 in purchases within the first 3 months of account opening. Miles can be redeemed for American Airlines and its partners flights.

2. Use your card for everyday spending

Miles are given for credit card spending, so transfer your major payments to credit cards. Under most programs, you'll earn miles for every dollar you spend as well as bonus miles or points for spending in specific categories like dining or groceries. So, plan your spending strategically. To maximize your miles, choose credit card with the high rate for everyday purchases.

For example, Discover it® Miles card rewards you with unlimited 1.5x miles on all purchases, while the Citi® / AAdvantage® Executive World Elite Mastercard® gives 2 miles for AA purchases. So, if you don't fly often with American Airlines, general travel rewards credit card will bring you more miles.

3. More ways to earn miles

Besides, there are lucrative deals that come and go, such as testing things or buying wine. Those you need to follow, which is best to do at travel-oriented sites. Finally, you can earn miles without spending a penny! Just fill out a couple of online surveys on sites that offer rewards for it and earn 100-1000 for a survey (it takes up to 20 minutes, but you can choose small ones that take no more than 5 minutes).

Important note, don't forget about miles expiration!

You should keep in mind that miles may expire after 18 or 36 months, depending on the card or frequent flyer program. The miles you earn with with the Discover it® Miles credit card never expire.

Overall, it might seem confusing, but earning miles is not actually that difficult. Investing some time and channeling your purchases may lead you to virtually free flights. Different credit cards reward you with different amounts of miles on your spending, and choosing the right card is the key to earning maximum miles for your purchases.