I've left what I hope are meaningful comments on other people's posts, and a note to let them know I've followed them, but I don't ask for follows in return. I want people to follow me because they enjoy what I write. If they're actually interested in the things I write about, they'll be more likely to upvote, comment or resteem. If they just want to swap follows, it's unlikely they'll read my posts so it's really of no value to me.
It's even worse when people send you a private chat message asking to swap follows, when you've never come across their work and have no idea who they are or why they are randomly contacting you.