A great way to make money online is through your blog. You can post comments on products you are marketing, add banners and use Google AdSense just to name a few. Blogs are great because you can post anything you want, and they are loved by the search engines. Also you can start one for no cost.
Let's start with posting your comments on products you are selling. First be honest. Only make favorable comments on products you feel are beneficial to your customers. This will go a long way in building trust among the people who follow your blog. On the other hand if you feel a product is a total rip off, let them know about that also. You should try to let them know all the benefits they will receive by having the product you are selling.
Most companies will give you some banner ads that you can add to your blog. You can also put Google AdSense on it. Just don't tell people to click on the ads.
The reason I stress not to tell people to click your AdSense ads is that will get you banned from the AdSense program. Here's how AdSense works. You get your free blog, post a couple articles on what ever your blog pertains to then sign up for AdSense. Once Google accepts you to the AdSense program they will place ads on your blog relevant to your blog posts. You get paid every time someone clicks an ad on your site.
The reason you can't sit there and click ads yourself or tell others to do it is that Google considers this click fraud (which it is). You should know that someone is paying Google for that ad being placed on your blog and they pay every time someone clicks that ad.
Go to blogger.com to set up a free blog. They walk you through the whole process including setting up AdSense on your blog.