If he speaks to you and flirts with you that's a good start, if he addresses you in person talk to him. As from a LOA standpoint you could always use Remote Seduction/Influence, Lanie Stevens has some good books on that topic. I've also read a book called "Manifesting Love" by Elizabeth Daniels and she has written some good methods to practice. Veronica herself has books that are a great, insightful read.
What do you want to happen with this guy? Would you like to go on a date? Would you like him to buy you a coffee? Once you set your intention live as if you have it. Neville Goddard says we should live in the end, so what would you be doing once you have your desire? Live in your imagination and it'll become your reality.