Step 8: Write a script
You: Beautiful night for stargazing, isn't it?
Her: Yes, it is.
You: I wonder is we'll see any shooting stars tonight. (pause) If you see one, you get to make a wish, you know. What would you wish for?
Her: Oh, I don't know, maybe a pony, or a million dollars, or ...
You: If I saw a shooting star right now, I would wish that we could be this happy for the rest of our lives.
I know, it's a pretty short script, but you need it to get your timing right. You should also know what you want say to her when you ask her to marry you, but that is outside this instructable and totally up to you. Here's mine: "Darling, if you will grant my wish, I will try to make your dreams come true. Will you marry me?"
Yes, these words might sound sappy sweet, but of all the times in your life, this is when you want to use them!