Anything other than signature campaigns and gambling.
A bit saved is a bit earned. So save your money by not clicking on any of the signatures of the people posting in this thread.
Bitcoin is a digital currency so you can make it up with the help of Internet and systems. You can earn Bitcoin through various Bitcoin related websites present all over the Internet. These are easy to navigate and you can easily earn bitcoin from those sites. If you have enough money then you can buy some bitcoin from different online sites. Or you can trade your stuffs for Bitcoin signature campaign is another way to earn bitcoin. It is most easy and trustable method. You can also earn bitcoin through gambling.