How to break into a niche?

You mean setting up an adwords campaign?

I've been thinking about something like that.

I tend to cluster together groups of long keywords as I am not prepared to start a campaign with the expensive terms. You will not get so many visitors but they will be focused.

for example

"Golf clubs" would be very hard to get noticed

"buy left handed golf clubs" would have fewer searches but they are keen to purchase. I would find ten similar keywords around this theme and that would be one ad group

(I haven't checked these numbers - it is an illustration)

It depends upon the niche, but some competition is easier to get past than others. If you were targeting something like credit cards, finance, weight loss etc, where there is a lot of money to be made, your competition is going to be tough because they want to keep earning the money they are already. They won't tolerate a young upstart coming along and stealing their traffic, so you will have a real fight on your hands.

However, there are easier niches to target that still have many millions of results in Google, but those results are not so competitive and you will have a much better chance of getting by them.

Its horses for courses in this game. Generally, the easier the niche, the less you can expect to make from it, although there are exceptions and finding them is not impossible.

No IM'er worth their salt will tell you what those niches are, of course. They might sell you an ebook that claims to reveal well paying niches, but if they were really so good, they'd make more from working the niche than selling an ebook.

Finding a great niche is something you'll have to do for yourself, because when you think about it, if you found the goose that laid the golden egg, would you give it away?