Regardless if you need to earn some fast cash or we're just talking about making money in the grand scheme of things, there's an important psychology that needs to be mentioned before getting into the strategies. If you study Freud's model of the mind, you'll discover the Psychic Apparatus. It's the three-part construct in your mind that controls all of your behavior.
Become a virtual assistant. Virtual assistants perform a wide range of services for their clients, all of which can be completed online. Depending on the day, they may open and reply to emails, schedule online work or blog posts, write mock-up letters and proposals, or perform data entry. You can look for virtual assistant jobs on sites like UpWork.com and Problogger.net.
One of the cool things about Google AdSense is that it's so easy to get set up. If you have a blog or website, you can sign up for a free Google AdSense Account. From there, Google will give you a unique code that you will paste onto your website. Google takes it from there, tracking your page views, traffic, and earnings on your behalf. There is no upkeep or maintenance to get this thing going, which makes it a no-brainer if you have a website already.