How do I completely block someone from contacting me on the internet?

[HI!]

And hopefully it'll also kill any desire to contact me through phone or mail or personal visits?

[Excessivesmoke496]

Ignore them. Soon they will get tired of it and leave you alone.

[carmen]

order a TRO on him/her Temporary restraining order
then if he/she violates that they can serve ALOT of time believe me
then they will also get a permanent restraining order.

[T K5]

I would suggest changing your email accounts (it's a pain--especially if you receive email from this person at work, and especially if you receive important messages from others at this address--but most emails have a "block mail from this address" feature of sorts, where all email received is ignored--but doesn't help much if this person emails you from "multiple accounts".

Also, if a problem, I would suggest setting up NEW social networking sites that you already have (MySpace, Facebook, Twitter, etc., IF you have these), preferably, use a NEWLY created email account (preferably without a photo--but include if you must--set to PRIVATE---and eventually contact all your "friends and family" to direct them to your new site. HOWEVER, if anyone is associated with--or is in frequent contact with this "unwanted contact", then you will have some problems.

But, these are helpful suggestions.

Also, if "snail mail", or postal mail, is sent with this person's return address, AND "First Class" postage (such as cancelled stamps) has been applied, you have the option of Crossing out YOUR NAME (personally, I would "black it out" with ball point pen AND Sharpie marker, but don't tear through the envelope!), and writing on top of envelop: "REFUSED--RTS" in capital lettters at the top of this UNOPENED MAIL. Circle this, highlighter this with highlighter, and draw arrow to return address, and place in your mailbox--or better yet, one of those official blue postal boxes.
Better yet, assuming that the postal mail does contain [first class postage AND return address AND you refuse to open it], you might want to keep all such mail for awhile--maybe even for 2 months--and do this with EACH piece of mail--except write--"REFUSED--RTS-ADDRESSEE UNKNOWN". Again, be sure YOUR NAME is complete unknown, and your writing is not recognized by [the unwanted contact-]-you could have somewhat else write it for you if you wish.
(By the way, "RTS" stands for "Return to Sender".)
As for phone messages, if changing your phone number is not a feasible option, you might want to get an answering machine service, or answering machine (depending on how many calls you get).
Be sure to get put on the "Do Not Call Registry" to avoid MOST telemarketers within 31 days of request, if not already on this list. You could change your greeting to reflect the fact that you "screen your calls" if you wish.
These are just my suggestions, if you wish/need to resort to them.