I have a few DVD's but the more efficient way is over internet. I usually go on crunchyroll.com or Animecrazy.net the thing about that website is that the quality is kind of low but they always have Animes up to date so I love it 3nodding Hulu is a good place to watch animes too.
I stream it online, whether it be through Netflix, Youtube, or some other website.
I do own one series on DVD and three other series are stored on my external hard drive. My boyfriend gave those to me from his computer.