A simple phrase, Oh that reminds of when. And then go into DHV story telling. After you get enough IoI's you can start to talk about her. Find out what her qualities are and reward those that you genuinely like by complimenting them. If she says she likes to travel, you can talk about where you have been, what happened to you there etc. NEVER COMPLIMENT ON HER LOOKS, COMPLIMENT ON HER PERSONALITY
On a side note:
I prefer to use more direct openers, something like: Please stop checking me out so obviously, or Are we gonna keep flirting from distance or actually start talking... ..or even something like:I won't have sex with you on first date, given that you got some IoI's from her before

If i see a girl likes me I love to pretend she wants me so hard and joke her about that. They love it
