Search for blogs that cover similar topics. Use a search engine and the search bar on blog hosting sites to find blogs that cover your topic or related topic. Read a few blog posts from the most popular ones, that show up high on the search ranking, have the most comments, or display a readership of 20,000 or more. Get an idea for how much interest and competition there is.
In-depth tutorials are great for getting links and social shares. However, they can also be a great way to earn money on your blog. There are a number of ways you can make this happen - include affiliate links for the products you use in your tutorial; promote your own products in the tutorial; write a tutorial to promote an advertiser's product (just be clear that it's a sponsored post), etc.
Once you setup your account on AdSense you will be given a code to add to your blog. This code will automatically display advertisements on your blog from companies who are part of Google’s advertising network. You may see ads from small companies related to your topic, or you may see ads from large companies that are completely unrelated to your topic.