Create a blog and start posting
You do not need a full-fledged website or download a blogging software such as WordPress, you can get a free blog at WordPress or BlogSpot. All you have to do is sign up and start publishing posts. You have to make sure that your blog does not sit idle for long, as you need to keep updating it from time to time. Otherwise Google will not pay attention to it and your search engine ranking is bound to remain low.
Boost blog traffic for contextual ads
Blogs that attract massive traffic usually make money. You can get contextual ads if your blog traffic is huge enough as advertisers will want to get ads on your posts. You can give space for a banner to advertiser, but it is generally done with blogs that have high page rank and publish posts on popular topics. Advertisers will typically assess your blog’s traffic stats and content quality.
Google lets you use AdSense on your blog and make money through it. When you create a blog, your search engine ranking is usually nil as the pages of the blog are not indexed by Google. Once Google indexes your pages and your posts start appearing in search results, you can think of getting AdSense on your blog.
Google will post ads of different websites to your blog, keeping in view the size of traffic and content quality. When people click on these ads, you get some money in return. But recall that this can only be done when your blog is updated regularly and is worth reading. If blog posts are popular, more and more people will read them and some of them may click on the ads, helping you make some money.
You can get in touch with platforms like CommissionJunction or LinkShare, as they will let you insert promotional banners to your blog, helping you earn money when someone buys from that website (the ad you have posted).