I did an almost YA novel one time.
I employed the use of my oldest daughter to help me work through the teenage elements of it and really knit together three foster sisters. I really played up what I had experienced as a foster parent, the odd-girl out situation when a foster child first comes to a foster home and how she is discounted by the others... for awhile. Then as bonds grow, they become close. The novel came across as realistic because I watched the dynamics play out in my own house. How sisters will squabble all the time with one another, like "she played with my Barbie Dolls", but then at a playground have another kid push one of them, and instantly all four sisters would surround the poor kid and ask, "Did you just push my sister"? It was always neat to see how close and protective they really were of one another even if the bonds were not biological.
All this was woven into a pretty good story anyway that had a pet bunny that was almost a main character until its own. It played a HUGE role in the plot, final action scene, and even the ending.
My daughters (age 11. 16 and 17) have all asked to read it, and they can someday, but it had a sex scene in it, :-(
I would just include a fade to black type of sex scene, BUT the adults in this novel had a huge love/hate relationship so the sex scene was a HUGE part of the plotline. That is typical of my novels though. Unless the sex is truly monumental to the story, I do not include one. With this novel, it completely changed the dynamic of the two adults, and cited the sisters to band together to stop them from being together.