>Find an appropriate image
1. These things work best when the girl is looking at the camera. You'll also want an image that isn't too cluttered so you have space to add your caption. First pic related.
2. Another option is if the girl is alone and has a dreamy look on her face. This works for thought bubbles (is she fantasizing about her brother/dad/son/goat?) 2nd pic related.
3. With images of multiple people, it works better if everyone's saying something… EXCEPT the guy, if we're supposed to imagine it is the viewer. See pic#3
4. If you have sets of a particular girl, they can be perfect for telling a longer story, such as in pic #4
5. Be creative. Pic5 is a joke, but there's no reason you can't do a sexy vertical comic