Online "experts" are always offering conflicting keyword advice. This is because different keywords are good for different reasons. Once you know the factors involved, you can decide which ones are best for your web site.
I have a page of my backpacking site optimized for the term "dirtbagging." I think I get half the world traffic for that keyword, but that only means ten visitors a month. I was new to online marketing when I put up that page. Obviously you need decent keyword demand to get much traffic, but demand is just one factor.
My Keyword Advice
1. Make sure there is enough total demand for a keyword. This will vary according to the nature of your site. If you are making a few cents per visitor an average, you need more traffic than sites that average a dollar per visitor. I won't optimize for a keyword that is searched less than a few hundred times per month.
2. Look at keyword demand/supply ratios. Last month there were 289,000 searches for "fishing," but with 35 million results showing up on a Google search for the term, can you compete? Probably not. A Keyword term like "bass fishing tips," with 3,700 searches, and 31,000 results is a more likely winner.
3. Consider total supply. Google shows 300 results for "dirtbagging," 15 times the 20 monthly searches for the term. Still, it is easy to get on the first page of results for the term. A keyword with a demand of a million, and a million search results has a better ratio, but can you really get on the first page of search results? Whatever the ratio, you have to be able to compete against the total supply. Nobody will find you on the tenth page of results.
4. Consider the type of keyword. Good search engine placement is one thing, but what type of visitor are you getting? Who's more likely to buy something or click on your affiliate links, a searcher for "fishing stories," or "fishing poles?" You'd probably make more money with the second term, even if it had half the traffic.
5. Look for keyword variations. My site www.IncreaseBrainpower.com was optimized for "brain power." I later found there was even more traffic for "brainpower." I have since optimized for both. By the way, both spellings are in the dictionary. Look for odd search phrases too, but be careful about optimizing for misspellings and bad-grammar keywords, if it might hurt the reputation of your site.
5. Consider the value of keyword ads. If you rely partly on pay-per click advertising, like Google's Adsense program, for revenue, you may want to consider the ads that will be diplayed for a given keyword. Ads for "surveilance cameras," pay four times as much per click as those for "hidden cameras."
6. Consider your interest and expertise in the topic represented by the keyword. Do you want to write a page on that topic? Can you deliver what a searcher of that term is looking for? Giving real value while doing something you enjoy - that's my final keyword advice.