This is such a big question that it is hard to give an answer, especially when you dont know that much about online marketing.
I am a full time internet marketer and will give you some tips.
1. Do NOT hire an SEO firm to do anything on your site. More often than not they will completely rip you off and give you all sorts of recurring packages you dont need because they know that you have no knowledge about what exactly they are doing.
I have my own team of SEO guys who work for me full time, but there is a difference between knowing exactly what they are doing and how much it costs and not knowing this.
2. You have to know what kind of keywords, markets you are trying to target. You cant just build a blog, write all sorts of posts and then expect that you are going to magically appear on the front page of google for various keywords.
You need, on site optimization, off site optimization (diversified backlinks), solid market research and good content.
If you are just doing this as a hobby the easiest way to get more exposure is just do some social bookmarking. Digg, Stumbleupon etc. Just go in there and put up some interesting bookmarks about your site.
If you are doing this to make money, you really need to immerse yourself into Internet Marketing and understand the dynamics of it. It is very easy to think IM is just a gold mine because of all the "make 2000$ a day adds" and even though those numbers are higly realistic for people who know what they are doing, people who have not immersed themselves will never be able to do so.