I heard about Melty Blood and thought it looked cool, so I did some research on it, and decided to play the original Tsukihime. Fell in love with it, loved the story, played the Melty Blood story mode, and from then on I decided to finally watch Fate since I knew it was the more popular of the two series.
For getting into Fate, I saw a video about games that were similar to Persona, and saw Fate/Extra. I played it, really liked it, couldn't get past Shinji, forgot about the game, played it again, and now I've finished Extra and Extra CCC (both with Caster), and I'm now doing the CCC route with Gilgamesh.
Everything in the Nasuverse is sooo cool...and I love how history is incorporated, since it's my favorite subject. I'm trying to read Kara No Kyokai right now (but I'm bad with reading books )