Cailean's flirts start out pretty tame since he's kind of "once bitten twice shy" about romance after the whole Masalina debacle and has made it clear to the PC that he doesn't want to jump into anything right away.
These are PC initiated flirts.
Daydream about Cailean
(Cailean's mouth captures your attention and you find your mind wandering...)
(You imagine him nuzzling your neck, his warm lips pressing tiny kisses up your throat, his tongue exploring the curves of your ear.)
(As you drift back into awareness, you realize from Cailean's puzzled gaze that you have been staring at him.) Did you want something, <CHARNAME>?
P1: Maybe later.
P2: No, just lost in thought.
Hug Cailean
(You approach Cailean from behind and as you reach to slide your hands around his waist, he startles and whirls around to face you, weapon drawn and ready. He turns red with embarrassment when he realizes who it is.) I am SO sorry <CHARNAME>! Old habits are hard to break! (He takes you in his arms until you both stop shaking.)
However, in case you do get tired of playing it nice, you do have the option of teasing Cailean.
Tease Cailean
(You put two fingers to your lips, kiss them and then place them on Cailean's mouth, allowing them to linger for just a moment. You catch his bottom lip as you slowly let your fingers drop away, pulling it slightly. Cailean takes a deep breath and exhales with slow deliberation, shaking his head.)