Bing SEO guide is the official Microsoft guide for SEO with BING, as found on Bing Webmaster center:

The following are official recommendations that might help Bing’s MSNBot (The Bing web crawler, a program that scans websites and indexes their content, such as text, documents, images, and links, for searching.) and other web crawlers (A program that scans websites and indexes their content, such as text, documents, images, and links, for searching. The web crawler used by Bing is also known as MSNBot.) effectively index and rank your website. Bing has also provided a list of techniques to avoid if you want to make sure your website is indexed.
Bing SEO technical recommendations

Use the following techniques to ensure your website is technically optimized for MSNBot and other web crawlers:

* Use only well-formed, HTML code in your webpages. Make sure that all paired tags are closed, and that all links open the correct webpage. For information on validating your HTML code, see either HTTP Compression and HTTP Conditional Get test tool or W3C Markup Validation Service or use a comparable tool.
* If your website contains broken links, MSNBot might not be able to index your website effectively, thus preventing people from reaching all of your webpages. For information on finding broken links on your website, see the Help topic for the Webmaster Center’s Crawl Issues tool.
* If you move a webpage, set up the webpage’s original URL to redirect people to the new webpage. Indicate whether the move is permanent or temporary. For more information, see What to do when your website is relocated.
* Make sure MSNBot is allowed to crawl your website and isn’t on your list of web crawlers that are prohibited from indexing your website. For more information, see Control which webpages on your website are indexed.
* Use a Robots.txt file or tags to control how MSNBot and other web crawlers index your website. You can use the Robots.txt file to prevent web crawlers from crawling specific files and folders. For more information about the Robots.txt file and the Robots Exclusion standard, see A Standard for Robot Exclusion. This site might be available in English only.
* Keep your URLs simple and static. URLs that are complicated or that change frequently are difficult to index as link destinations. For example, the URL www.example.com/mywebpage is easier for MSNBot to crawl and for people to type than a long URL with multiple extensions. Also, a URL that doesn’t change is easy for people to remember and bookmark. That makes your webpage a more likely link destination from other websites.
* Watch for malicious software (malware). Links to webpages on your website that lead to malware on third-party websites or contain malicious content, such as a maliciously corrupted image or document file, or a harmful ActiveX control or JavaScript, will be disabled and highlighted as Malware in Bing results webpages. See the Help topics for the Webmaster Center’s Crawl Issues tool and Outbound Links tool to learn how to find these detected malware issues on your website. See Remediate detected malware to help rid your website of all malware.
Bing SEO content guidelines

The best way to attract people to your website, and keep them coming back, is to fill your webpages with valuable content in which your target audience is interested. The following guidelines can help you create a more effective and popular webpage:

* In the visible webpage text, include words users might choose as search query terms to find the information on your website.
* Limit all webpages to a reasonable size. Bing recommends covering one topic per webpage. An HTML webpage with no images should be under 150 KB.
* Make sure that each webpage is accessible by at least one static text link.
* Don’t put the text that you want indexed within images. For example, if you want your company name or address to be indexed, make sure it isn’t displayed only inside an image of your company logo.
* Add a Sitemap, which helps MSNBot to find all of your webpages. Links that are embedded in menus, list boxes, and similar elements aren’t accessible to web crawlers unless they appear in your Sitemap. For information on creating Sitemaps, see the Help topic for the Webmaster Center’s Sitemaps tool.
* Keep your website hierarchy fairly flat. That is, each webpage should only be from one to three clicks away from the default webpage.
Bing SEO forbidden stuff

The following techniques aren’t appropriate in terms of attempting to gain higher ranking with the Bing index. Use of these techniques might actually adversely affect how your website is ranked within Bing, and might even cause your website to be removed from the index.

* Attempting to increase a webpage’s keyword density by add lots of irrelevant words. This includes stuffing ALT tags that users are unlikely to view.
* Using hidden text or links. Only use text and links that are visible to users.
* Using techniques, such as link farms, to artificially increase the number of links to your webpage.

Here are some more information by Rajesh Srivastava, Principal Group Program Manager, Bing:
Bing’s SEO principles

SEO is fundamentally about creating websites that are good for people. The most basic advice we can give for achieving optimum rank for your site in Bing is to do the following:
Develop great, original content (including well-implemented keywords) directed toward your intended audience
Use well-architected code in your webpages (including images and Sitemaps) so that users’ web browsers and search engine crawlers can read the content you want indexed)
Earn several, high-quality, authoritative inbound links

As you can see by the links, much of this material has already been discussed in-depth in the Webmaster Center team blog in our ongoing column, search engine marketing (SEM) 101.

The type of SEO work and tasks webmasters need to perform to be successful in Bing hasn’t changed—all of the legitimate, time-tested, SEO skills and knowledge that webmasters have invested in previously apply fully today with Bing. Moreover, investments in solid, reputable SEO work made for Bing will bring similar improvements in your website’s page rank in other search engines as well.

Ultimately, SEO is still SEO. Bing doesn’t change that. Bing’s new user interface design simply adds new opportunities to searchers to find what the information they want more quickly and easily, and that benefits webmasters who have taken the time to work on the quality of their content, website architecture, and have done the hard work of earning several high-quality inbound links.
Key content and tools for performing SEO with Bing

To keep up with the latest and greatest information coming from the Bing Webmaster Center team, we recommend that you follow and review the following content:
Review the Bing official guidelines for successful indexing document for various recommendations on technical and content issues as well as known problems that can affect your site’s rank
Visit the Webmaster Center blog to keep up with the latest information from the team (you can even subscribe to our blog’s RSS feed to automate this process)
Register all of your websites with Bing Webmaster Center tools, where you can use our tools to see all sorts of data to your website pertinent to webmasters
Participate in our Webmaster Center user forums to ask questions and provide us with feedback

We look forward to working with you as partners in helping our mutual customers find the information they seek on the Internet.

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