One of the ways to begin making money online is by blogging and placing Google Ads using the Adsense program. Before placing any ads on your blog, I'd suggest working on building significant targeted traffic. You'll want to identify certain thresholds for measuring how successful your marketing campaigns are for your blog. Additionally, you may say that 10, 100, 1,000, etc. visitors a day are thresholds that you are going to achieve. The thresholds you set are important for you right now. As you're doing this you'll want to communicate with different advertisers in your target audience and see what type of traffic they look for before advertising on a blog.
In creating a successful blog there are a few things to consider. On the Internet "Content is King." Content could come in the form of text, audio, video, photos, etc., but at the end of the day "Content is King" Second people will come to your blog upon you creating and updating your blog with useful relevant content. For instance, you mentioned several subjects, in order to optimize your blogs for search, you may want to separate your blogs by subject.
Ideally you'll want to update your blog once a day, more if possible. Make your post personal, yet relevant to your target readers. Give your readers information they can't get anywhere else mixed with your own commentary. Quote other reliable bloggers and sources creating backlinks to other websites and blogs. This will show that you are not selfish and recognize leaders within your space (subject). Your readers will respect you and other bloggers will reward you by mentioning you in their blog, post, forum or site as well. Focus on great relevant content. "Content is King"
After a few weeks of consistent blogging, register your blog with the major search engines such as Google, Yahoo and MSN. There are other sites where you'll want to register your blog with to increase inbound links. Become an active participant on forums related to your subject. Create a signature line with a live link going back to your blog(s).
If you use some of these methods and are consistent within 12 months you should see significant increase in traffic to your blog(s). Below are a few of my blogs.
moneyonline.blogspot.com
gojawar.blogspot.com