so much of the new testament is rooted in principles and the assumption of maturity. we put fences around our yards when our children are young to protect them from danger. as they grow older, they mature and no longer require fences.
the bible does not specifically delinate sexual actions because it is rooted in principles and the assumption of maturity.
kissing or hugging are not sinful. there are principles, however, that would allow them to lead to sexual immorality. maturity sees the danger and uses caution (without a fence saying that kissing is wrong).
other things, though, like intimate touching, oral sex, etc are more obvious, inasmuch as they are always (with extreme exceptions) done in private because people understand it is a private issue. other principles clearly draw attention to the sexual line that is crossed