Sexual purity is big deal. It always has been and it always will be. I believe it was among the things of what was lost in the fall. Adam and Eve's first response when hiding from God because of their wrong doing and minds being open to evil had to do with their "nakedness" - their sexuality (c.f. Gen 3:7). Sexuality presumably up to that point had not been perverted in any way, it was completely pure. Yet after the fall, sexuality was marred. And so it remains to this day. Everyone will come to relationship with marred sexuality and a fallen sexual nature, and many people will come into marriage with marred sexual pasts and experiences. But praise be to God that he is a redeemer and calls the things that are not as though they were (c.f. Rom 4:17). Sexual Immorality: The Christian dating and/or romantic relationship MUST be pure (c.f. Gal 5:19-21; Eph 5:3; 1 Tim 5:2; etc.) for purity even transcends dating and characterizes all romance, even marriage (c.f. Heb 13:5). The questions always come up about how far is too far? I mean I know that I shouldn't have sexual intercourse, and God wants me to technically be a virgin when I get married, but what about other forms of affection? What about kissing, etc.? I will put my position straight out: I believe that any sexual physical activity (defined as any contact that creates sexual stimulation) outside of marriage between a man and a woman is sin. "Technical virginity" and biblical purity are not the same things. To define sexual immorality think of it's inverse, sexual morality. Sex that is moral is that which God has made moral, sex between a man and a woman in covenant relationship together; marriage. So sexual immorality is what is not sexually moral; all sexual activity and thoughts outside of marriage. Kissing: A common barometer that I tell others to use (who are often curious people who have not explored their sexuality much and tend to lack any conviction about the power of sexual temptation and it's snowballing properties) is by asking them if they have ever kissed their father or mother. If they have ever kissed their father or mother in any sexually impure way. And if they always kiss their boyfriend or girlfriend exactly as they do their mother or father. For anyone being honest, the answer is obviously no. But I ask them to probe further, why don't you kiss them the same way as a family member? Because again, if we are honest, the relationship is not the same. It is romantic, so our kissing is romantic. Now can I come out and say that all kissing cart blanche is a sin between a couple. Well no, of course not. But what I am confident in saying, is that I think it's a stupid idea for a Christian couple, a pandora's box of sorts. But let's continue to probe, why do we have such a difficult time with this idea anyway? Why is it so difficult to deny ourselves here? Why do we clamor and claw to keep our right to kiss? Because we are selfish. Because we like it. Because it makes us feel good. Because it helps us to feel connected to another person. Which is a beautiful thing that God has made, and that He has made exquisitely good. But he has made it for a man and a wife (c.f. Gen 2:24; Mat 19:5; Eph 5:31) and not to happen with "prostitutes" (anyone not your spouse) (c.f. 1 Cor 6:16). ​Unfortunately I have had extensive experience with all of this. Becoming a Christian after my life had been marred by sexual sin and then experience the pain of sexual sin as a Christian with another Christian (largely due to that devilish question "how far can we go and still be ok?"), it took me many years before God helped me to build the conviction that I would not even kiss my wife to be until we stood at the alter. My now wife and I did just that. I was in my early 30's and she was in her late 20's. It was her first kiss. Ever. This looks like foolishness to the world (c.f. 1 Cor 1:18). And indeed we both had some that looked on in utter disbelief. Some who thought that a man my age who was not married and did not have a girlfriend must not be attracted to women. But God chooses the foolish things of this world to shame the wise (c.f. 1 Cor 1:27-31). Talking About Boundaries: (also see DTR) So how should you talk about where you are going to put your physical boundaries? I think it should be as soon as two people become and item or an exclusive couple (before then there shouldn't be much to talk about). My wife and I had this boundary talk the day I asked her to be my girlfriend. If this type of conversation cannot happen in a mature and healthy way, then I would argue there are some bigger problems at hand, like whether or not the people are really ready to take on the responsibilities of dating. But this type of conversation brings in other considerations as well. Not just physical boundaries (though very necessary), but also emotional boundaries such as how much will we see each other, talk on the phone, text, etc. What type of situations will we allow ourselves to be in and which ones will we not? For instance my wife and I decided that we would not talk on the phone after 11pm, we would not be in a domicile together alone, and we would tend to not take long car rides or road trips together alone, etc. Emotional Immorality: Just as we can engage in sexual immorality, I believe we can also engage in emotional immorality. Emotional immorality is perhaps a bit more difficult to define and spot, but we must fight for awareness. For in the Christian dating relationship where the emotional connection continues to grow without the physical intimacy growing equally, pressure can ensue and the "emotional pacing" of the relationship becomes a factor. In view of simple discipleship principles like denying yourself (Luke 9:23) and not being mastered by your flesh but led by the Spirit (1 Cor 6:12; Gal 5:16-18), you must think about restraining yourself in the amount of emotional connection that you allow to develop throughout courtship. Don't start off texting several times a day, don't start off always hanging out together, in essence don't act like you are married until you are married! The 'pacing' of a relationship is vital for it's health throughout the course of courtship, for if you allow the relationship to become to emotionally intimate too quickly you run a great risk of experiencing great frustration and tension because you have reached this glass ceiling that you cannot move passed. It is always easier to hit the gas pedal in a relationship than it is the brakes. If you find yourself having moved to far to quickly in the relationship and you need to hit the brakes and slow down the pace, it usually proves quite difficult because you already have a trajectory and expectation of what the relationship is like, so I advise to start of slow and make sure you have the big picture in view. This is especially important if you are younger and know that marriage is not likely a reality for several years (i.e.. you are a student in school or something). This is something in which your tribe becomes vital and is invaluable. Other helpful blog posts on the topic: Principles For Drawing Boundaries | Kept My Virginity, But Not My Purity