A lot of people look for technical tricks for SEO and ignore the big picture. You need both. Your SEO (and business) strategy is every bit as important as SEO tactics.  There are more than 200 [SEO factors][2] that go into rankings, but here are a few of the more important SEO factors that I've experienced, both tactical and strategic:

 - **Have a website worth visiting.** If
   your website isn't designed for users
   first, most of the time it won't do
   well in the search engines. 
 - **Make your site crawlable.** Don't rely on Flash or JavaScript
   navigation. If you need to use
   JavaScript, use it to enhance an
   existing (X)HTML menu, not create it.
   You won't even need a sitemap if your
   site is crawlable in the first place
   (but it doesn't hurt). RSS feeds also help you get crawled.
 - **Do your keyword research using Google's [Keyword Tool][3].** I guarantee that you're missing out on traffic opportunities if you don't do this (and most people don't). Take 5 minutes to make sure
   that your content is hitting the most
   popular search terms for its subject
   matter. It's worth it.
 - **Make a bigger website.** Backlinks matter and internal links from your
   own pages count. The easiest, surest,
   and most efficient way to get
   backlinks is to increase the number
   of pages on your site. The bigger
   your search engine footprint, the
   more weight you have to throw around. This is one of the reasons blogs are recommended for SEO.
 - **Get your title right.** You get 65 characters to create an on-topic
   incentive for the user to click on
   your search engine listing. Use the
   opportunity wisely. Your best keywords should be in the title. However, it's not just
   about using the right keywords; 
   it's also about catching the user's
   attention while still signalling that
   your page is going to be relevant and
   helpful to them. Use Michael
   Masterson's Four U's Method: Be
   Unique. Be Useful. Be Urgent. Be
   Ultra-Specific. Stronger titles use
   more U's. Remember that your title is
   often used by social media sites to
   link to your page as well.
 - **Get your anchor text right.** Use keywords that are also helpful to
   your users. Never use the infamous
   'Click Here' or 'More...' text as a link.
 - **Get a handle on duplicate content**. It's far too easy to
   create duplicate content.
   `http://example.com`,
   `http://example.com`/,
   `http://www.example.com`, and
   `http://www.example.com`/ are all
   considered different URLS. URL parameters also create duplicates:
   `http://example.com?a=1&b=2` and
   `http://example.com?b=2&a=1` are both different URLs. Use Apache or
   whatever server you're using to
   manage your redirect rules so this
   doesn't happen. This needs to be a consideration from the beginning and should be solved both programmatically and with server redirects.
 - **Don't waste time asking for links.** There is no bigger waste of
   time and money, IMO, than emailing
   other websites offering to do link
   exchanges. Think about the time spent
   searching for relevant websites,
   emailing, responding, and
   implementing a link exchange. What's
   your hourly wage? Now think about
   economies of scale and how many times
   you have to do that to make a
   discernible difference for every page
   of your website. There is no way that
   you can possibly come out on top.
   There are easier ways to get links.
 - **Make your site sharable.** All those little social media widgets?
   They might be annoying, but when used
   properly, they make it easier for
   your users to share your content. The
   caveat here is proper context.
   Privacy policies, terms of use,
   registration, and other pages of that
   ilk are probably not good candidates
   for a widget.
 - **[Viral content][4] works.** But you need to use it wisely. Not every
   announcement on your site is going to
   be or should be viral. It has to make
   sense and it needs to be
   well-thought-out. Ask yourself
   objectively, *why would someone link
   to this?* If you can't think of a
   good answer, you should go back to
   the drawing board. Again, the 4 U's
   help here.
 - **Incentivize linking.** A great way to kickstart a viral campaign or even
   a more moderate but steadily growing
   external link profile. Think contests
   and giveaways, but also think
   Stack Overflow's badge widgets.
 - **Build a community** An audience of loyal readers will link to and share
   your content naturally.
   User-generated content increases your
   website's footprint and also
   incentivizes linking.
 - **Remember the big picture.** Why are you doing SEO in the first place?
   What is the purpose of your website?
   It's easy to focus so much SEO that
   you lose sight of what you're trying
   to do. If you're trying to make money
   with your site, don't forget that you
   also need to focus on the usability,
   the design, the copy, the offer, the
   product, the checkout process, etc.
   SEO is only a small part of that.

If you're interested in more details, I wrote an article on my website about [basic SEO tips][1] which you can reference for more info.

**Edit**: Incidentally, one of the reasons Stack Overflow does so well in the search engines is because it has an enormous community that continually produces keyword-laden pages. It gets a lot of the basic tactical SEO right too, but this is an excellent example of big-picture thinking that most people ignore. SEO is built into the design of the community as an extension of the way the community functions. That wasn't an accident.

  [1]: http://www.virtuosimedia.com/articles/seo-in-10-minutes-search-engine-optimization-tips-for-beginners
  [2]: http://moz.com/search-ranking-factors
  [3]: https://adwords.google.com/o/Targeting/Explorer?__u=1000000000&__c=1000000000&ideaRequestType=KEYWORD_IDEAS#search.none
  [4]: http://www.virtuosimedia.com/articles/secret-formula-how-to-write-viral-content-for-your-website