Calling a guy is hard. What if he doesn't pick up? What if he does pick up? These are just some of the possibilities that keep us from hitting that last digit of his phone number. But then you finally do work up the gumption to make the call, and his voice comes on the line -- and you have no idea what to say next.
Don't let awkward silences be the death of your conversation. Before you even pick up the phone, think of one or two things to bring up during the conversation. It doesn't have to be big, although if you're feeling brave and want to ask him to the prom, go for it. Ask him about things you're both involved in, like Spanish class or math club. If you're worried you'll draw a complete blank when you actually get him on the phone, jot down a couple of reminders. But whatever you do, don't write out a word-for-word script. Just let it come naturally.