Very easy and free 100 miles with Delta, Northwest, Lufthansa and 16 other companies after filling out a simple form. More details available at Mobile Miles.
One thing regarding the phone number you enter. DO NOT enter your own or change the ‘+372′ prefix for Estonia! Just add 7 more random digits and hit submit. You will then get a confirmation page.
You can try doing it again and again for all the programs that you earn miles/points with; however be sure to enter a different phone number every time. You can also use a different email every time, should you choose to do so, but it is not necessary.
Have a nice clicK life,