Defining some terms:

From Wikipedia the definition of keyword is: An index term, subject term, subject heading, or descriptor, in information retrieval, is a term that captures the essence of the topic of a document.

When someone wants to find something related to his problem or question, he types in a keyword or better yet a keyword phrase. More experienced internet users type in specific, narrow phrases that define what they are looking for.

You have read that you need to create a blog...now is the time. You have heard that having a blog attached to a website, or just having a blog will bring you traffic. That's true, but if you want to be successful, you need to compete in a niche that isn't overcrowded...and more importantly, you really have to like the niche you are going to be working in you will be thinking about, writing about and dreaming about it for some time.

I can't help you with whether you will love the niche. That is a choice that I cannot help you with. However, I do have something to say about overcrowded niches.

Overcrowded means that if you do a search in say, "internet marketing", with quotation marks, you will see there are about 39,200,000 results in Google. I am going to tell you, that you cannot compete in that broad niche.

You will have to find a smaller portion of internet marketing to compete in.

Here are some suggestions:
retail internet marketing
internet marketing pricing
internet marketing branding
internet marketing trends
internet marketing jobs
internet marketing forum
future of internet marketing

You may not like these suggestions, but if you keep digging long enough with the proper free tools, you will find a niche where there isn't too much competition. You don't want to go too far afield, though. If you choose a niche that is too small, you won't have enough traffic.

Where did I come up with these niches? One of the free keyword tools that I use is the Google External keyword tool. (You will find it on the list.) These particular suggestions show that they don't have a large number of people searching for these terms.

You will be spending hours and hours promoting your blog, so make sure that you do a good job of researching your niche. Use MANY of the free tools that I list to help you to absorb, think, study and wallow around because this is an important topic.

I have seen, many times, that people spend three to six months in a particular niche and make no progress. Finally, you realize that you cannot compete with a long-established site if it is in a broad niche.

Don't waste your time working and promoting, until you have defined a small, but important area in which to concentrate your efforts.

I suggest that you use these tools listed and spend about two weeks or so researching. This is probably as important as finding a soul-mate. It may take lots of searching, but you will have the tools with which to do the searching...that's easier than finding a soul-mate.

After all, if you don't have a strong desire to communicate in a particular niche, it will be work. If you love your niche, it isn't work.