Its like baking a cake ... a little of this a few of those a little of that. You need a good chunk of text, your target keywords in your anchor text, a decent title with your keyword(s) is also essential, and a few more things and then you have your cake. But just having a site optimised for the SE's wont bring you good results, you need people linking to you with your keywords in their anchor text.
The more contested the keywords, generally the more link backs required and from a lot of different c-classes and different ip's. Also a gradual increase on your inbound link trades helps ... not one huge dump of 1000 links to your site, because google notices those kinda things and can penalise you for it.
The bigger and more content rich your site is, and the more people who link to it, the higher you tend to climb in the SERPS
Thats generally it