Tomorrow I'm going to ask the girl of my dreams to be my girl freind?

When should be the correct time to ask her to be my girl freind ? We're both in my schools marching band so tomorrow we're going to a city called Blackwell in Oklahoma should I ask her before band rehersal during band rehersal or after school befor we get on the bus and we get 3rd quarter off during the foot ball game 3rd quarter us right after half time or while we eat ? I'm just so nervous when I about ask her to be my girl freind and when I about I don't say any thing we known each other for a while and I really like her more than friends were in the freind zone right now and I've been told by 3 pepole she likes me too