Technical guidelines of Google

Use a text browser such as Lynx to examine your site, because most search engine spiders see your site much as Lynx would. If fancy features such as JavaScript, cookies, session IDs, frames, DHTML, or Flash keep you from seeing all of your site in a text browser, then search engine spiders may have trouble crawling your site.
Allow search bots to crawl your sites without session IDs or arguments that track their path through the site. These techniques are useful for tracking individual user behavior, but the access pattern of bots is entirely different. Using these techniques may result in incomplete indexing of your site, as bots may not be able to eliminate URLs that look different but actually point to the same page.
Make sure your web server supports the If-Modified-Since HTTP header. This feature allows your web server to tell Google whether your content has changed since we last crawled your site. Supporting this feature saves you bandwidth and overhead.
Make use of the robots.txt file on your web server. This file tells crawlers which directories can or cannot be crawled. Make sure it's current for your site so that you don't accidentally block the Googlebot crawler. Visit http://www.robotstxt.org/faq.html to learn how to instruct robots when they visit your site. You can test your robots.txt file to make sure you're using it correctly with the robots.txt analysis tool available in Google Webmaster Tools.
If your company buys a content management system, make sure that the system creates pages and links that search engines can crawl.
Use robots.txt to prevent crawling of search results pages or other auto-generated pages that don't add much value for users coming from search engines.
Test your site to make sure that it appears correctly in different browsers.
http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=35769

Pagerank sculpting

People think about PageRank in lots of different ways. People have compared PageRank to a “random surfer” model in which PageRank is the probability that a random surfer clicking on links lands on a page. Other people think of the web as an link matrix in which the value at position (i,j) indicates the presence of links from page i to page j. In that case, PageRank corresponds to the principal eigenvector of that normalized link matrix.
No PageRank would ever escape from the loop, and as incoming PageRank continued to flow into the loop, eventually the PageRank in that loop would reach infinity. Infinite PageRank isn’t that helpful so Larry and Sergey introduced a decay factor--you could think of it as 10-15% of the PageRank on any given page disappearing before the PageRank flows along the outlinks. In the random surfer model, that decay factor is as if the random surfer got bored and decided to head for a completely different page. You can do some neat things with that reset vector, such as personalization, but that’s outside the scope of our discussion.
Now let’s talk about the rel=nofollow attribute. Nofollow is method (introduced in 2005 and supported by multiple search engines) to annotate a link to tell search engines “I can’t or don’t want to vouch for this link.” In Google, nofollow links don’t pass PageRank and don’t pass anchortext [*].
So what happens when you have a page with “ten PageRank points” and ten outgoing links, and five of those links are nofollowed? Let’s leave aside the decay factor to focus on the core part of the question. Originally, the five links without nofollow would have flowed two points of PageRank each (in essence, the nofollowed links didn’t count toward the denominator when dividing PageRank by the outdegree of the page). More than a year ago, Google changed how the PageRank flows so that the five links without nofollow would flow one point of PageRank each.

http://www.mattcutts.com/blog/pagerank-sculpting

Search Categories in Yahoo

To change the type of search you click a search category link ins the search box and make the results you see even more specific. Selecting one of the search category links gives Yahoo! Search instructions about what specific kind of search results you would like to see:
Yahoo Images: Searches for images, photos, illustrations, and icons from all over the Web and presents results ranked by algorithm.
Yahoo Video: Searches for videos from all over the Web and presents results ranked by algorithm.
Yahoo Directory: Directory search results are sites from the Yahoo! Directory and are ranked by algorithm. The Directory is a human-created and maintained library of web sites organized into categories and subcategories. Sites that participate in Directory Submit pay for an expedited review for potential inclusion in the Directory.
Yahoo Local: Local search results might contain listings that paid for placement. Those listings are separated into the Sponsored Businesses and/or Featured Listings sections of the page. Listings within the Local results might have financial relationships with Yahoo! but have not paid for placement.
Yahoo News: News search results are sites derived from multiple sources that you can rank either by algorithm or date.
Yahoo Shopping: Yahoo! Shopping helps you find products and compare prices from different merchants selling the same item. Yahoo! Shopping does this in part by searching through millions of products offered by thousands of third party merchants. Most merchants included in Yahoo! Shopping pay for placement of their product offers in resulting listings. In general, the order in which Yahoo! Shopping search results are displayed is determined by an algorithmic ranking and relevance is a key factor used, although payment by participating merchants along with other factors can affect the order of Yahoo! Shopping search results. Some Yahoo! Shopping search results may include products from merchants that submit content to Yahoo! Shopping for review and inclusion in the Yahoo! Shopping database. These merchants pay for inclusion of their content in the Yahoo! Shopping database, but participation in this paid inclusion program does not guarantee placement or ranking of search results. To add comprehensiveness, some Yahoo! Shopping search results may include free results generated from millions of web pages discovered, crawled and indexed by the Yahoo! Shopping web crawl process

The services that you can expect from an SEO company

When you want your site to become one of the top sites being seen on a search engine’s results page for your category, you will probably need the help of an SEO consultant or an SEO USA expert.
Getting an SEO company to work on your website will help get your site to show favorably when certain keywords associated with your site are searched for on Google and Yahoo.
The keywords that are researched for use on your websites can also be used for the URLs that you will be utilizing for that added punch when it comes to generating results and for showing higher on these pages. Keyword research is probably one of the toughest parts of SEO since this is the backbone of the search engine world and is what people use to find you and other sites similar to you.
They will give you advice on what keywords will be good for your site as well as what your content should probably be about.