For a majority of the girls I try to talk to, either through text or Snapchat, I can never get past the first few minutes of a convo. I'll either send them something, and they won't reply, or they'll reply and have a convo for a minute or two, then not reply.

Am I doing something wrong? What's some good way's to open up a conversation that will keep a girl interested and not feel weirded out? How can I better my chances of getting a reply?

EDIT: I forgot to mention that a lot of these girls I've never had much conversation with, if any at all.