How do I send a ping?

What is a ping?
The example url I use is this one: http://wordpress.org/development/2006/04/wordpattern

Pinging a post on another blog from your post is very easy. All you do is link to it.
The link in this screenshot goes to the post above.

That will cause a ping to be sent.

See also: How do I stop self-pings?

Q & A
Can I ping and trackback?

No. If you send both to one place, the trackback will fail.