I once found a comic by randomly running a search for "fruit" on smackjeeves. I still follow it.
When I make friends with other artists I support their work, and if a really active fan (comments, likes, shares) has a comic, I am very likely to start recognising their name and checking out their comic. I check out the collections and look through the comics on the front page of tapastic, search by genre, as well as find comics in the forums. It's pretty random!
I have found a lot of comics through twitter, and in specific there is a twitter chat that has actually gotten quite large, so I encourage you to take part in #webcomicchat, happens every Satuday at 8:30 eastern time. Check the tumblr out here, and the webcomicchat bot is here. Checking out the hashtags webcomics or ReadMyIndieComic turn up comics as well!