(First of all, there are many amazing and wonderful tools to help shorten the learning curve for you to get into profit more quickly with building a blog, and I have several of my personal favorites scattered around on my blog here.)
But is a few short words, making money with a blog is simply by looking at it as a 'showcase' or storefront in a way, as you know how in real life, outside the walls of the internet, if you want to buy shoes, you will go to a shoestore - or if you want pastries, you would hardly go into a pet shop...
Same way online... people are searching online for stuff, every seciond of every day.... if you are blogging about pets, then you will want the links on your site to go to pet items.
It would be silly to write an article about your Aunt Bonnies amazing pumpkin desert on your blog about pets - not only silly but actually the search engines will look at that and because nothing really matches up, they will pass over it whereas if everything is related to pets, and someone googles something like 'allergy pet skin care' and you have a blog post about something related to 'allergies and skin care' you just might get that traffic which can turn into a customer for you if your blog is related to what they are actually searching for.
I have seen blogs that have everything but the kitchen sink on them and then they wonder why they do not get traffic from the search engines!
Here is a simple tip that will get you more targeted traffic in a matter of days:
Write a post on your blog every day for a week - and keep it all very similar, and yet have it be fresh new content - for instance, let's use the pet care one since we seem to be on that subject!
One day, you write a blog post about 'pet skin care' - the next day it could be ' allergy free pet skin care' and the day following, you might do one that says ' sensitive pet skin care', etc, etc, and ping your blog each time you add a post.... if you have never pinged your blogs - go to pinggoat.com and follow the steps there - it is easy and free to register for it.
You should notice an increase in traffic very quickly with that one little trick... go one step further and write a brief article using the same keywords and link back to your blog with them - submit your articles to places like ideamarketers.com , goarticles.com and ezinearticles.com ...