Go up to the person have a nice start of conversation. U know like what's up what r u going to do this weekend. Did u hear about that one kid. That kind of thing. Then ask the person about valentines day and what their going to do. Then if they say really nothing ask them maybe u would want to do something with them. And then ask them the big question. Simple as 1,2,3. 1. Start friendly conversation. 2. Talk about the event 3. Lead up to asking them. Wish u luck :) P.s it's always good to wait a little while before just incase they ask. Some can be shy a need a little push.
if he doesnt have a gf walk up to him act sexy and say i want you to be my valentine and get like all up close on him and if he says something kinda wierd like what are you doing then just say come with me and you can find out and you can guess what happens from there