You need to start by ensuring you’ve done your keyword research, everything hangs on the viability of the keywords you’re targeting. If you can do this even before you’ve bought a domain, then you can even ensure your targeted keywords are part of the domain name itself.
Try to use a system of writing webpages that enables you to have your keywords in your URL, in the title of each page.
Make sure the system you’re using enables you to change the meta tags, make sure the page title, description, keywords are all included (and different for each page).
When you write on one page, ensure you are continually targeting your keywords, focus on just 1-2 keyword phrases per page, if you’re trying to fit in more than that, then break the page down into two separate pages.
Make sure Google knows your site exists – best done by having other sites linking to you. Look at how you can build back-links to your website (don’t pay for them).
Your content needs to be keyword targeted and relevant.
Time …. time is important, the longer your site is live, the more Google thinks it’s a good site.
Time …. don’t expect it to happen overnight, work regularly on building up your site and its back-links, checking your keyword relevancy/density and tweaking it.
Read some free books online and you’ll find they all tell you the same. Once you’ve got the basics, then you can move onto tips/tricks/techniques etc, but if the basics aren’t right then you’re wasting effort.