I always wait for almost anything to finish first before I purchase anything. Almost everything literally.
Anime - I wait for the DVD-Bluray boxset to come out and I also usually wait a year or so for the price to come down a little.
Videogames - I never buy videogames until the second edition comes out, or GOTY edition that comes with all the DLC content and other bullshit, and even then I wait until the price comes down or it is on sale on steam.
Comic Books - I generally don't buy them issue to issue, instead I wait for the grahpic novel versions come out. Which is usually about 6-10 issues put together. I find this a much more enjoyable read as comics are very short.
Television shows - I always wait for the seasons to be finished and get the seasons on DVD afterwards, if the show looks interesting. I don't like very many TV shows, so I don't have many TV shows in my collection. Game of Thrones is one example that I wait for the Season to be over. Walking Dead is one exception, I watch this show as they come out. Season 3 starts tonight actually.
Novels - This is a messy category...I usually prefer to read book series after the series is over. Although I pick up a lot of recently written series that are just starting, I prefer to wait and these days I am beginning to wait for series to finish first more then ever. 'Song of Fire and Ice' being an example as I have not yet started reading these, I'll probably start as the final book nears completion. Instead i'll go back and read books that came out years ago and read older series. 'The Belgariad' series is an example of this as this five part series came out in the 80's.
~This is unfortunate as I am a low level writer myself and wish to support others like me, but must save the monies. Oh well.