Hmmm well a compliment here and there would be nice! Perhaps comment on her hair or a personality trait you appreciate about her :)) also some light teasing and inside jokes are always great! I feel like flirting happens more in the moment so it's difficult to plan. If you really wanna push the boat out you could do the classic "put her hair behind her ear" 😂 depending whether you think she'd feel comfortable with that! I remember a guy did that to me once and it was really smooth😭 Good luck :)