Niiche blogs are blogs that are focused on one topic.

This is what Wikipedia says about niche blogging:
Niche blogging is the act of creating a blog with the intent of using it to market to a particular niche market. While it could be argued that all blogs are, in some form, a niche blog, the term as it applies to marketing refers to a particular kind of blog.

Choosing a Niche

You really need to have a passion for the domain you choose and you need to know it very well. Think from the beggining how popular the subject is, what target will you have, what competition exists, how will you monetize your blog.

The way you choose your site name

It must be original, not to be confused with other blogs (popular) from the same niche.
A few basic things that you need to know

• If you want a professinal blog you’ll need to have your own domain name & give your money on a good hosting;
• Constantly publish articles: depending on the niche you choose, pitch a number of articles you’ll post per day or per week and don’t break it. Be careful not to make long breaks, always have a few drafts saved which you’ll publish or complete when you need;
• Good writing skills, easy to follow;
• Visual identity: make a good-looking logo, theme, business cards;
• Don’t optimize your blog in excess: SEO SPAM IS BAD! You could read WordPress SEO - 6 basic tips for better SEO if you want to learn how to optimize your blog.
• Don’t hide your contact form, you need to be easily contacted;
• Always have a few banners in your hand, ready to be sent;
• Install plugins which will fit your niche. (ex: Community links feed)

First of all, you need to have quality articles, because content will always be the most important! Come with something new: exclusiv news, the speed you publish information, the way you present the information (ex: Opinions from your own experience).

Follow your competition: other blogs and websites from the same niche, the more they are the better it is. Find their weak points & their strong points. Learn from others mistakes, use their experience to your advantage, think how can you be a step in front of them. NEVER take material/information/ideas without asking or without crediting them!

Search for forums related to the niche you’ve chosen. Register on the most active ones, follow the discussions, socialize, post constantly, contribute with new and interesting information. DON’T spam! Don’t register on forums only to promote your blog, it’s not nice. You’ll probably be banned.

Search for people that are interested in your niche on other blogs or websites (through articles or comments), on forums, on social networks (ex: Facebook, Myspace, Twitter). You can invite them, if they have experience or if they have something interesting to say, to write a guest post.

Read magazines and newspapers related to your niche. You never know where some new ideas come from, ideas that you can adapt to online. Contact the press to suggest a collaboration between your blog and the publications. It’s not hard at all to contact them at press conferences or to search for their e-mail or phone numbers. Explain them who you are and ask them to put you in contact with someone that is taking care of your niche. Of course, do this only when you come with something relevant, new, which will attract attention. After you get in contact with them you could suggest:

• Write a few words about your blog;
• If you are expert in a domain or you constantly come with new materials, they could credit/cite you in articles;
• You could offer to have a rubric in their pages (or websites), regardless of the size. In exchange, you could offer ads on your blog.

If there are events related to the niche of your blog and you can go, my advice is don’t stay home! You could be a media partner and promote that event, to request in exchange ads on the flyer/website of the event/in the press releases related to that event (logo/banner/URL).