I think this is the wrong site to post about guy gal thing. Coz most of the ppl give advice are guys. lol....
See, if you're a gal and this guy suddenly jio you out then big surprise and stuff. The gal whom the threadsetter like but doesn't know that he likes her will think....whoooaaa....this guy wants something outta me (which is true lah) but she's gonna get intimidated by him....Then if she not interested, both will be embarrased.
But if he goes ahead to organise a big party with all her friends, include parents, siblings, and everybody that matters to her etc. U know....buy drinks and get food, make place nice nice, get dirty and start the fire for the bbq (for example), think of a bday program, blah blah blah.....
In essence, work really really hard to just make her day a wonderful one. Ask for no return other than her smile. She will be very very surprised about the hard work the guy put in. Even if not interested, also might get interested.