Since I'm really into art, I've subscribed to LOADS of art channels. It's always fascinating to watch how others work and can be very inspiring. There are also times where I can learn a lot from watching their videos as they may know techniques I don't, it gives me the motivation to try it myself. I've actually improved quite a bit in some areas of my own art because of it, which is fantastic and I'm very thankful for it

I always hope that my videos can do the same for someone else ^^
For non-art channels, I usually aim for more humorous channels. Typically light-hearted stuff and not mean jokes. I like Tobuscus, JacksFilms, CinemaSins, TomSka, Awkward Spaceship, etc. It's great to laugh, especially when I need it

I also love learning and hearing about news (domestic and global) so I'm also subbed to channels like VSauce, CrashCourse, SciShow, CGP Grey, Phillip DeFranco, etc.
Before I sub to channels I usually watch at least a few videos to really get the feel for the person and how they do their videos. It's hard to judge a channel based off one video and I hate watching trailers, they almost never tell you anything and it's impossible to really understand the channel from that alone.