Starting

Firstly, you will have to locate what content you wish to remove, this should be fairly easy considering it is you. Put your head in the mind of a Doxer and try googling your emails or alias' or even using sites such as:
http://www.pipl.com/
http://www.411.com/
http://www.usaphonelookup.com/
http://www.peoplefinders.com/
http://tineye.com/

Once you have found whatever you need to remove, we can now proceed!

Removing

There may be many forums and accounts that are accessible by you, an easy was is to simply login and alter the information being displayed. Also I would suggest changing the email and password to that account as well.

The hard part is attempting to remove information that you don't have access to.

Pastebin pastes are fairly easy to remove, just report it and say that it contains personal information and within 24 hours the paste should have been removed as requested(http://pastebin.com/contact).

If you're already Doxed on paste sites such as SkidPaste, you can simply pay $10 BTC to remove that paste, it may seem a lot but if you care about your privacy you will pay it.

Any other sites that you don't have access to, you should contact the owner and they should also respect that and remove if request. If you are having any problems getting the contact information then run a who.is check on the domain and you should get some contact information that way.

A common website used is whitepages.com, if you're on this you can simply edit your information and fill it up with false information.

Removing Cached

Google:
https://www.google.com/webmasters/tools/removals?pli=1

Bing:
http://www.bing.com/webmaster/help/bing-content-removal-tool-cb6c294d

Yahoo:
https://help.yahoo.com/kb/search/remove-search-results-yahoo-search-sln4530.html

Use common sense when requesting and if it isn't very serious information, then make up some bullshit lie :)

Conclusion

Hopefully this tutorial has helped you.

Helpful Links you may have missed:

Lookup Sites
http://www.tinyeye.com/
http://www.peoplefinders.com/
http://www.usaphonelookup.com/
http://www.pipl.com/
http://www.411.com/
http://www.whitepages.com/

Remove Sites
https://justdelete.me/
http://forget.me/