Mirror websites 

Hosting of multiple websites all with conceptually similar content but using different URLs. Some search engines give a higher rank to results where the keyword searched for appears in the URL.

URL redirection 

Taking the user to another page without his or her intervention, e.g. using META refresh tags, Java, JavaScript or Server side redirects

Cloaking 

Cloaking refers to any of several means to serve up a different page to the search-engine spider than will be seen by human users. It can be an attempt to mislead search engines regarding the content on a particular web site. However, cloaking can also be used to ethically increase accessibility of a site to users with disabilities, or to provide human users with content that search engines aren’t able to process or parse. It is also used to deliver content based on a user’s location; Google itself uses IP delivery, a form of cloaking, to deliver results.
A form of this is code swapping, this is: optimizing a page for top ranking, then, swapping another page in its place once a top ranking is achieved.