Aside from surveys, Minecraft codes are sometimes given out for free online, such as on Facebook and YouTube. For example, in January 2011 Deadmau5 posted several first-come, first-serve Minecraft codes on his Facebook page.
The easiest way to find free Minecraft codes without having to partake in surveys is to search for codes on YouTube. YouTube users often give out codes in videos or provide links to websites that give out codes for free. It is important to search for videos and websites that have working, up-to-date Minecraft codes because the codes will not work if they have already been claimed.