I use a mix of adsense and affiliate products. You can google more information on this, but affiliate placements is basically where someone else is selling a product that is in the topic/niche of your blog. You then include the product in your blog and get a percentage of each sale. You can do this by making a review or just mentioning it for example. I use this because it ads more value to my posts- it may help some people that weren't sure about buying it before