Site about "acne" here is what some people consider long tail:
To me these are keywords that will have competition.
acne treatment reviews
back acne treatment
acne scare treatment
Some may even consider these as good ideas:
How to get rid of acne
What causes acne
The problem with these questions are that they are common which means there is sure to be plenty of sites with articles based on this exact phrase.
These are the phrases I would go after :
What are some homemade remedies to get rid of acne scars?
Can I use acne scar medicine along with my regular acne treatment?
I have acne on my face and back, how can i get rid of it easily without using much money?
How can I tell the difference between teenage acne and adult acne?
What acne wash or natural remedy worked for you?
I recently gave this same advice to a wf member just yesterday.
I told her hey you could make a site about acne as seen above and further explain a site like this could be monetized using not only adsense but also amazon and click bank products.
I would use a stand alone squeeze page to sell "acne no more" e-book from click bank
Use adsense on all other pages.
Have a products page using amazon where they could buy Clearasil or some kind of acne products.
This method takes a lot of content to be truly effective but I guarantee you'll make money from a site like this.
A better way would to go after high paying keywords because you would only need about 2000 visitors a month to make anywhere from 100.00 to 200.00 a month.
You may not even need that much content with the second approach. 50 posts may do it or 75 I don't know because there are to many variables to consider.
There was something else I wanted to say but forgot what .
Edit: I remember now I was going to say I also make comments on my own blog that are related to the post itself.
Example: post title "how to get rid of acne fast"
I would post comments like "I got rid of acne quickly" or "what's the fastest way to get rid of acne".
These comments sometimes bring in extra traffic through google search