A blog is the most common way of doing content marketing. However, you could also try videos as in YouTube. You can choose whatever fits your product or service best, what you are most comfortable producing. Ultimately written content is great as its the cheapest and it can be reused in a newsletter, ebook or turned into a video.
Other forms of content marketing is providing a free tool that your customers can use. Something like a calculator, a spreadsheet or something similar.
As an example look up HSBC bank and their expat tools. They built an entire platform that helps people who want to work abroad. They have a small survey that can help you choose the next place you should work and other useful info. They did this to promote their banking services and the public loves their approach.