How far can a Christian couple go before marriage?
If you are truely Christian then read your Bible, all your answers can be found there. And if you are truely Christian you already know the answer to your question. You are only hoping to get permission to be naughty. As for what is acceptable in the modern world, the same values of Christianity apply now the same as they did 500 years ago. A sin is still a sin. You should wait to do anything more than kissing. Waiting ensures that your wedding night be a special remembrance for both of you and that is the way it should be. Two newly married souls discovering each other for the first time.
