The most reliable way is to configure the server to send out a redirection instruction when the old URL is requested. Then the browser will automatically get the new URL. This is the fastest and most efficient way, and is the only way described here that can convince indexing robots to phase out the old URL. For configuration details consult your server admin or documentation (with NCSA or Apache servers, use a Redirect statement in .htaccess).
If you can't set up a redirect, there are other possibilities. These are inferior because they tell the search engines that there's still a page at the old location, not that the page has moved to a new location. But if it's impossible for you to configure redirection at your server, here are two alternatives:
* Put up a small page with text like "This page has moved to http://new.url/
-- please adjust your bookmarks."
* A META Refresh tag won't work for all browsers and can break the "back" button. For example:
<meta http-equiv="Refresh" content="[x]; URL=[newURL]">
which will load [newURL] after [x] seconds. This should go in the HEAD of the document. But if you do this, also include a short text saying "Document moved to [newURL]" for other browsers.