dropped site

As in topic - can anyone describe how I can find find high quality, valuable, dropped domain in my niche? What tools should I use? What should I look for while searching? Any experience share/exchange is more than welcome :-)

Hi so anyone in the anime niche? I don't care.... Anyhow Animeseason.com is going to be dropped by owner.. I've been trying for months to buy it off him. He's going to stop with it because he doesn't enjoy it anymore(video's with ads) and the pop ups ads etc. He doesn't like the DMCA...