Don't use 302 redirects (AVOID)
A HTTP 302 server redirect is supposed to be used when a page is only temporarily moved from one location to another on a server. Spammers use 302 redirects because that gives them many more URLs to the same final page and thus many more ways to get to that page.
The only time you should use a 302 redirect is if you have ugly URLs with lots of parameterson them. The 302 redirect tells the search engine that this is not a permanent redirect, but rather an alternate URL. For all other redirects you should use a 301 redirect instead.
Don't make constant minor changes to content (AVOID)
While you want search engines to see that you update your content, making minor changes (like correcting spelling errors, or changing 10 or 20 characters) implies that you're just trying to get the updated date changed. This looks like you're trying to fool the search engines into thinking that you update your pages more than you actually do.
Do spend time updating your pages, but make the updates substantive.
Don't separate content artificially (AVOID)
Don't display different content based on IP, browser type or version, operating system or whatever. This is very tempting for most Web designers, as it's a way to show you know how to write JavaScript or another programming language. But it can look like you're trying to trick the search engine - showing it something other than you show your readers.
If you really must display alternate content based on some artificial measure, create separate Web pages for each, rather than using the same URL for all the content. Or, keep the content that is different as minimal as possible, don't build an entire new site for each IP or browser type.
Don't violate copyright or other laws (AVOID)
Most search engines have terms of service that ban sites that break the law. Copyright infringement is the easiest way to break the law on the Web. Don't assume that because something was posted to the Web it is legal for you to reprint it, get permission or link to the article instead of copying it. Search engines will ban your site if you regularly steal content or break other laws.
Don't duplicate content on your site (AVOID)
One trick that spammers like to use is to create one page and then post it in numerous locations, both on one domain and on others. The idea is that if there are enough copies of the page, it will get seen by more people. But search engines don't like duplicate content as it's a waste of space on their servers and does not provide good information to their customers. If a search engine suspects your site is spamming them with multiple copies, your site could be banned.
Don't use robots.txt to ban large portions of your site (AVOID)
In general, using a robots.txt file to keep certain areas of your site off-limits to spiders can be a good idea. But if you ban significant portions of your site (more than half), search engine spiders may mark your site as "forbidden" in general and simply stop spidering your site as often. And if your site is spidered less often, fewer pages will be added to the directory and updated in rank.
Don't write bad or incorrect HTML (AVOID)
Most search engines don't deliberately discriminate against badly coded pages, but if the spider can't read the page because the HTML is bad, then it won't get indexed. Make sure that you validate your HTML regularly and that any issues there are don't affect the page being viewed by a simple user-agent or screen reader.
Don't use frames (AVOID)
Frames and search engines are not a good combination. While search engines are getting much better at reading framed websites, they still don't tend to rank as well as non-framed sites. And even if you get decent ranking, you might not get the clicks because the search engine doesn't know what to display as a title or description of your page.
Don't create Flash splash pages (AVOID)
Search engines can't read images, and they see Flash as a giant image. Flash and search engines don't mix well. If you don't have extensive alternative HTML that displays when Flash is not enabled, then your site won't rank well in search engines. Be sure to test your site with a browser with Flash disabled to find out what the search engine sees. You might be unpleasantly surprised.
Don't write Flash-only sites (AVOID)
If you're going to use Flash on your site, you must have an HTML version that displays when Flash is enabled. It can be tempting to put in just a single line or two of HTML as your non-Flash alternative, after all, you've done so much work on the Flash site. But since the search engines only see the HTML, that's what they'll rank, and you won't rank high with just a tiny version of your site in HTML.
If you must use Flash as your site, and you want to rank well in search engines, you need to be prepared to write your site twice - once in Flash and once in HTML.
Never redirect to another domain (AVOID OR GET BANNED)
Redirecting to another domain is not a 100% guarantee that you'll be banned from search engines. But it is a very common spammer trick used in conjunction with doorway pages and cloaking. If you set up a redirect that goes to a new domain, you need to write it as a 301 HTTP redirect, not a 302 or meta refresh. This tells the search engine that this redirect is permanent, and they should change to the new domain in their directory.
Be Careful Redirecting to New Domains - You Could Be Banned
Since this trick is commonly used by spammers, it's a very good idea to avoid doing it. Search engines can be very hard to get back into if your site is banned by mistake.
Never link invisible images (AVOID OR GET BANNED)
Invisible images are images that are 1x1 pixels in size and cannot be seen by the naked eye on a Web page. Since links are given some priority in ranking a Web page, linking images that cannot be seen by your customers appears to be aimed only at search engine spiders.
Don't Link Single Pixel Images - Your Site Will Be Banned
This is similar to hiding text or displaying different content to search engines than to your customers. And don't assume that search engines can't read CSS or HTML tags that resize full-sized images. If you do this to optimize your pages, your site will be banned.
Never include invisible text on your pages (AVOID OR GET BANNED)
Hiding text by making it the same color as the background color may fool your customers, but it won't fool search engines. Another variation of this is where you make the font size so small that it's unreadable by the naked eye.
Don't Hide Text - Your Site Will Be Banned
Search engines understand CSS and font and background colors. They also recognize that a font-size of 1px is not going to be readable. Text that is hidden from your readers but visible to search engines is considered spam and will get your site banned.
Never create doorway pages (AVOID OR GET BANNED)
Doorway pages are very simple HTML pages that are written to optimize heavily on one or two keywords or keyword phrases. And they are programmed so that search engines spiders see them, but regular readers are taken to the real site.
Don't Use Doorway Pages - Your Site Will Be Banned
Doorway pages are designed to trick search engines into thinking that the site has a specific keyword relevance that it may or may not have and they are pages meant to be seen only by the search engine. So, most search engines will ban sites from their directory when they discover you use them.
Never display different content to a spider than customers (AVOID OR GET BANNED)
This is often called cloaking because it is an effort to cloak what your site delivers in something that might be seen as more palatable to search engines. It can be very tempting to use cloaking, but while it might give you better results at first, search engines don't like it.
Don't Cloak Websites - Your Site Will Be Banned
Search engines want to provide a resource of information that is real, not something that has been doctored to give artificial results. When they discover that your site is cloaking, it will be removed from the search directory.
Good readers always drop comments!!