One of the things I dislike is the reusing of overrated and overused songs in fanmixes. I've been guilty of that in the past but, I try to at least search for unknown and lesser used songs so it doesn't have this repetitive feel like every other fanmix does sometimes. That, and making sure the songs match the theme I'm going for in said mix (which is why it's kind of hard for me to finish one mix, haha).