Speaking as the Devil's Advocate, there are innumerable ways to make sure your website will be lost in the depths of the Google index. If your goal is to propel your online presence into obscurity, then we have all the state of the art methods to do so. We have neat little tricks most people spend several hours and thousands of dollars trying to reverse, but we list them here for you to implement them at will. Enjoy.
Hand over your website design to a colour blind dyslexic with no technical or creative aptitudes, and give them only a mouse and a monitor, no keyboard. Oh, and use a Microsoft product. Make sure the site is not intuitive in any way, and that it shares absolutely zero similarity in layout to any other website. Try not to use your company brand or colours.
Do not study search terms that may apply to your business. Knowing what keywords potential customers are using to search for your type of business is completely useless and a waste of time. Who cares? If you are just itching to know the popular keywords so you can make sure to disassociate your website from them, conduct a few Google searches yourself. Then eliminate the most popular words from every page of your site. Don't forget those META tags! Clear them out completely just to make sure there are no residual hits.
Render your homepage barren. When Google is searching for search terms, it reads home pages first, so most successful web presences prefer their site to be loaded with keywords. For your sabotage purposes, the less there is on your home page for search engines to index, the more likely they will ignore you. Short of completely removing the home page; consider posting a smiley face picture and nothing else. The Google bots will be thoroughly unimpressed.
Don't discriminate. Make sure all the images on your website are completely void of ALT IMG tags meant to offer descriptive dialogue for the visually impaired. If you want to make sure no one sees your site, make sure it is completely blank for the blind as well.
No directories. Many companies hire offsite individuals to submit their URL's to subject related directories to help with ranking. If your purpose is in decreasing rank, then do not submit your site to search engine logs, directories or registries. They are searched too, so it is important to keep your URL out of the lists. That goes for Google Places as well. If it is anonymity you are seeking, then avoid Google altogether.
Keep away from the latest technology in webhosting; things that might actually ‘save' your website. For example, a host that uses progressive security technology or intrusion detection is not for you. Some webhosts offer online video platforms, do not participate in these deals as they will only serve to improve page rank. Seek out a web host operating out of a third world nation, preferably where English is not the first language.
If your online presence is not a business, but actually for you personally, then there are a whole lot more things one can do to sabotage yourself. First choose a method of sabotage: obscurity or scandal followed by obscurity. For the first option, remove all social media profiles and blogs. Stop tweeting, facebooking, blogging, pinning and flickering. End it all. Combines with the tips listed above, removing social media profiles should do the trick. If your desire is to be involved in a scandal first, then there are a few options. Express some politically unpopular views in highly popular places, engage in a war of words with an A-list celebrity, or commit some sort of criminal act. When the hype is at its highest point, abruptly remove all social media profiles.
By now you must be wondering why anyone would want to carry out these tasks, other than in an experimental capacity. There may be a good reason for someone, somewhere; but our point here is to inform on exactly what not to do and what to look for in fostering a successful online presence. Hopefully your website doesn't experience any of these problems, but at least now you know what to look for. If you have not already done so, carry out solid keyword tests and make sure they correspond with those META tags. Optimize your homepage for maximum crawling and work with your webhosting service on security. It's just the tip of the iceberg, but every little bit helps get your site moving up the Google ranks.