Ladies Is This Too Direct?

I have the tendency to be straightforward with girls when i like them. Normally i will tell them that they are pretty or very pretty, not out loud just more like a whisper so they can hear it and no one else. I think i am a very nice guy but i still need to work on my charisma. Does this seem good? What else should i say? (I know a little bit how to start a convo)