‘Niche’ is a word you may have heard before in other uses but here is the common business definition of the term:
A niche market is a focused targetable portion (subset) of a market.
I’ll explain just what this means with an example. Say you’re a tea enthusiast. You could make a site about all teas in general but then you would be competing with many other sites. But this doesn’t mean you should give up, only that you have to narrow your topic by targeting a subset of the tea market. Let’s see if ‘earl grey tea’ is a market that we can compete in. How do we check? With freely available tools like Google Keywords, Google Insight and the standard Google search bar.
Using Google Keywords Tool
Visit the site: https://adwords.google.com/select/KeywordToolExternal and it should look something like this –

This is a powerful tool that lets us know how many times per month a particular term is searched on Google. Google is by far the largest search engine and so it will be the main source of organic, or search engine, traffic to your future site. Ranking well on the Google is very important but (generally) the more a particular term is searched, the more competition it attracts. Try typing ‘tea’ into the field and hit ‘Get keyword ideas.’

As you can see, the keyword ‘tea’ has a monthly search volume over 300,000, which means it is a highly competitive term. Any keyword with over 100,000 searches a month is ridiculously competitive. Even 30,000 searches a month is competitive. If you search ‘Tea’ on google, you’ll end up with a whopping 180,000,000 search results. Now let’s try the niche we thought of earlier, earl grey tea:

5,400 searches, that’s more realistic a target for beginners. You should try to find a ‘niche’ that has anywhere from 2000-8000 searches a month. Odds are, the more searches it has a month, the more websites there are out there trying to rank on Google for it. Now that we’ve found a niche (Earl Grey Tea), we need to check out the competition to see if we can easily produce a website that’ll rank better than the already existing sites for our term. To do this we simply Google our phrase ‘earl grey tea’:
Wikipedia is on top which isn’t unusual. Second place is a store while the third is a random about.com article about the famous tea blend. You can’t see it in my screenshot but a bit lower on the list is Memory Alpha, a fan site dedicated to Star Trek. Captain Picard drinks Earl Grey in the television show and the site’s short entry on it manages to make the first page. This means that we have a shot at ranking for this term. The #1 indicator that you have a ‘good shot’ at ranking for a term is the number of search results for it. If you look on the top right of the screenshot i took on the Google search above, you can see ‘earl grey tea’ only has 472,000 search results. Regular ol ‘Tea’ had a whopping 180,000,000 search results. Anything with less than 500,000 search results is what you should try targeting, as it should be fairly easy. If your idea or ‘niche’ has more than 1,000,000 search results, i recommend you throw it out the window and find something that has less competition. It’s not impossible to rank for a keyword with more than a million search results, but its certainly more difficult. Since this is most likely your first website, I strongly recommend you find a niche with less than 500,000 search results. 650,000 and below will do as well, but try to keep in mind, the less search results the better. You want to find a niche that is searched a fair amount of times and has little competition (Search results).
Market research isn’t complicated but it should never be taken lightly. Neglecting it puts you at risk of making a site targeting too broad a market and finding yourself unable to compete. This is a common problem with fan sites. A simple site with info and pictures of Natalie Portman may not be difficult to construct but the competition is stiff; better to target a lesser known actress like Jolene Blalock. A useful tool for comparing search traffic for two or more terms is Google Insights. (http://www.google.com/insights/) Insights can chart traffic by year, geographic location and other indicators. When we compare our two actresses we can see a stark difference:

Google Insights though is great for comparing two search terms, but it should not be used by itself. You should use the google keyword tool to see exactly how many times a keyword is searched a month before deciding that you want to make a website about it.
This was a long section, so let’s recap! Here’s everything you should have done before you click NEXT below to move on. Don’t worry at ALL what you’re going to put on your website, as that’s explained later in the section.
-Find a ‘keyword’ through the Google Keyword Tool that has somewhere between 2,000 and 8,000 searches a month with LESS Than 500,000 search results on Google.com.
-If your ‘keyword’ or ‘niche’ has more than 500,000 search results, DITCH IT! Find a new ‘Niche’ / ‘Keyword’!
Once you found a good ‘Niche’ with less than 500,000 search results with 2,000 to 8,000 searches a month, you’re ready to move on! Now we’re going to register a domain for your website. Click Next to continue!