-Sell your own product, service or information, if you have one.
-For blogger who don't have their own product, it's still possible to earn money from their blog thanks to many affiliate programs among which most popular one is "Google Adsense". But it's just one example out of hundred affiliate programs. if not thousand.

In short, make-money-blogging is doing step-by-step action: that is, you blog, bring traffic, PREsell your blog readers and finally monetize. Without bringing traffic and achieving PREsell, it is not possible to monetize your blog. That's why you need to keep in mind fact that make-money-blogging is step-by-step action.
Due to space limitation, I can't explain all detail. If you want to know more about each step, you can read it from article, what blog can make money?.

1. About topic, I'll do a little bit of research before I write. Have you heard about "keyword research"? There are free tools fit for keyword research. Not only for blog but for any kind of writings, if Internet is involved, I do keyword research first. For example, for this article, I took a little bit of time to find what kind of keyword people are using when they want to look for information about how to make money from blog. And I found people are using "make money blogging." This keyword research has two fold benefit. One is that it helps you fine what kind of topic people want to read. The other is that by using these keyword you'll have better chance to be positioned high in search engine result page.
2. About question 2, I'm thinking about what monetization method I'm going to use. Am I going to introduce an affiliate program, a book or place Adsense?
3. The purpose of asking question 3 was to emphasize word "PREsell". In blogging, though you want to sell something or want your visitor to click links, don't rush it.
What do you do if you see a blogger is doing nothing but a sales pitch. You leave him once and for all, don't you? So PREsell is key of how to write.It is something like creating a worm mind to your suggestion.
If you want to make money from your blog, start writing it only after you know what keyword is related your topic and what kind of monetization you can apply. This can make a huge difference.
If you want to know about how to do a keyword research, you may want to read this blog, Traffic to Blog: Keyword Research.
To sum up, a blog that can make more money is;
1. a blog talking about topic people want to read and this can be found by keyword research
2. a blog that uses the keyword in post so that search engine can easily pick up
3. a blog that PREsells product by creating warm mood.