He was asking how to check if a set retired or not. If it is not officially retired, then, technically, well, it is not retired...
go to http://shop.lego.com/en-US/
enter set number in the search bar, for example 7964
Result page will have the image of the set with "retired product". You will also see "retired product" if you click on that set
Also, on the same site, you can search using "retiring soon" filter, though there could be sets that pretty much everybody thinks they are "retiring soon", but TLG does not really have to confess, and there are no guarantee that set will actually go through "retiring soon" phase. It could go to "sold out" and/or "call to check availability", and straight to retired