The number 1 thing you must do is make sure you pick the RIGHT keyword to rank for.
Start with 1 keyword at a time. Make sure there is enough traffic for that keyword term and not too much competition.
Once you have found a keyword you develop one webpage of your site around that keyword. You use that exact keyword in the meta tags and content (keyword density). Don't overdo the content - just make sure the information on the page is fairly unique with about 10% being the exact keyword.
That's it for your site. Now you have to do some external marketing.
Google ranks your webpage based on 2 things:
1) Matching up the user's search term to your content
2) The number of external links coming into that webpage. (external links can refer to sites/blogs/forums/articles etc).
If there is very low competition, external linking doesn't matter. For instance, I registered a domain name using the exact keyword term for an affiliate product that I am marketing. Because I registered the domain before the product was launched and there was practically no competition I was on page 1 number 2 spot without even having the website up and running.
In the real world there is usually a lot of competition (and even if there isn't now there soon will be). So all you are doing with other sites/blogs/forums/articles is taking your keyword and pasting it as a link back to your site. In most cases you will need to give something back for them to do that (it could be write a comment, put one of their links on your page, write an article etc)
Hope that's not too hard to follow
