[header] How to date someone you previously rejected [title] Find out if they're dating someone. [step] If the person you've got your eye on has already, you might need to let them go. [substeps] Ask mutual friends about their relationship status check social media for clues recall if you've seen them out with anybody [title] Assess why it didn't work before. 
[step] There was a reason (or reasons) why you rejected them in the first place. It can be easy to ignore these issues if you haven't seen them for a while, or if you're just feeling lonely.