Delete What You Can First: If you can remember where you've signed up, go to those sites and delete your accounts. If you can't, going forward write down on a hard copy whenever you sign up to an online site. SmashGods says that, "commonly forgotten repositories of information include Flickr (and associated comments), old blogs, online resumes, FS (for sale) advertisements on non-expiring websites, want ads, personal ads, geneology webs and bartering sites."
SmashGods also warns that social networks, like Facebook, can be a confusing maze when you try to delete your account. A Facebook group ironically, explain the process here.
Use Webpage Removal Request Tools: Google and Yahoo! let people request that “private” information be taken down from websites, or request that webmasters remove pages with your name from indexing. "Ask.com includes an “AskEraser” that will completely delete your search queries and data from Ask.com servers, including: your IP address, User ID and Session ID cookies, as well as the complete text of your search query–all within a matter of hours."
Plead Webmasters Directly: Sometimes simply emailing the webmaster that has published your name is enough to get your John Hancock off the site. Some sites make it hard to find out who to contact though, which is where WHOIS comes in. Type in the url of the offending site in WHOIS and they'll pull up contact info for the person the url is registered to.
Get Help: Whether you don't want to take the time to sift through the web or in cases where a webmaster isn't helping your disappearing act, you can hire ReputationDefender. The company finds all info about you on the web, which you can then decide which cases you want the company to remove for you.
Bring in the Big Guns: If ReputationDefender hits a road block and you need someone who will send cease and desist notices to a site owner call up Chilling Effects. A bit pricier ($795 for personal use) RemoveYourName.com says their team will not stop working until your name is off of the major search engines, and their work is backed by a money-back guarantee. This will be a one time process.
Is It Imperative? Do you really need to leave that comment? Do you really need to sign up for yet another social networking site? Before you sign up, think about how important this is to you and if you still want to sign up take the following into consideration.
Use a Proxy: Hidemyass is a proxy service that lets you hide your online identity (your IP address) while using the web so sites can't record and use your info for analytical programs.
Use Pseudonyms: We are at fault of this just as much as any of you are. We don't know why, but when a site asks us our name, we never want to lie. But why not? Why does a blog need your real name anyway? You can simply use a fake name for all your online communications or you can use a fake name, address, phone, and email generator as we've previously posted about.