Why & How: How to make money with a blog

You can make money by adding advertisements to your blog or by using it as a promotional media. Even hyperlinks may be a source or revenues.

Advertisers and affiliate programs

Adsense

Blogger supports Google's Adsense to make money with advertisements while other hosts put a banner on your page and keep revenues to themselves... You can use Adsense on you own website too.
Datails in the next chapter.

Amazon affiliate
Help sell others' products. The principle here is that you make book reviews or just mention a book in your blog, providing you have registered to an affiliate program and there is a means for your visitors to click from your blog to Amazon which provides further information about the book.
There is a lot of steps to accomplish to create an account. Your revenues will depend upon both the clicks on the product from your blog and the percentage that is allowed to that product.

Blogads

With this service you can set the ad price. You register to a database that is parsed by big companies that choose the blogs to put ads for a set period. You don't depend upon the clicks: you give 20% of your revenues (you have fixed the price) to Blogads. You are free to approve or decline the ads that are displayed on your blog.

Commission Junction

Affiliate program for e-Bay and others.

Linkshare

This is another affiliate program where you gain money when net surfers buy product through your blog.

Making Money With Adsense

A single site managed by one person or a small staff can make thousand of dollars per day. See the Adsense FAQ for détails.
The Techcrunch blog was sold for 30 millions dollars in 2011.

How use Adsense

Using Adsense is very simple as you have just to select a format and put the JavaScript code on your HTML pages but it will be required several steps and a lot of time before to receive the first payment.
For 1000 unique visits, it is not uncommon to earn 3 dollars a day, but this amount can be increased substantially through referrals. In fact, several types of ads are proposed:

Contextual ads. These are images or texts in Ad Groups, selected by Google, whose subject is related to the content of the page. The higher is the relevance with the contents of the page and the higher will be the incomes.
Search ads. A Google search bar for your site or for the whole Web, will display ads on results pages and gains when visitors click on these ads.

How to improve earnings

The key to increase revenue, is in integration and placement.

The choice of ad format and the best placement are explained in this Adsense tutorial.
The integration consists in making the appearance of advertisements related to the design of the site.

What you should avoid

The idea of Adsense is you help advertisers to make money, and a percent come to you.

Never click on the ads on your own site, not even once to see if it works.
Do not ask family members to do so.
To not incite to click by some messages or other tricks.
Avoid confusion. Do not put images near ads so user may think the ads are for the images.
Do not place ads on pages without content.

See the list of things to avoid with Adsense for more details.

Other resources

Promote yourself or your product

Use the blog not just to start discussions with readers but to describe in depth your abilities and experience. You can make clients, or whatever you need to make revenues. You can establish yourself as an expert and be consulted by others that are not.
A blog can describe and promote your products as well if you are an enterprise or a programmer.

Work for others

Rather than writing you own blog, work for a company. You can also participate to a blog network. Numerous of them are willing to pay bloggers using a variety of payment models. If you have some success with you own blog, you can just put the offer to write for others on it. Or see at the BloggerForHire site.

Donation and sponsorship

If you are sure you blog is really appreciated by visitors, you can ask for donations, using Paypal or similar online bank to receive the money on your account. Sponsorship is a special advertisement model for a specialized blog, where a company gives money to a blogger and the blogger displays the logo the company.