September seems to be the month for free miles! The latest offer comes from a partner of Lufthansa Miles & More.
You can receive 350 miles by signing up to a German newsletter about cruises. It should only take you 10-15 seconds.
Click here. (use Google Chrome if you want to auto-translate into English)
Enter your name and email address where requested.
Choose the 350 miles button and input your Miles & More number.
You should receive an email from Kreuzfahrten asking you to confirm your email address.
Hopefully your miles will arrive within a couple of weeks, at which point you can un-subscribe from the newsletter.