Nobody is a porn star their first time, no matter how much porn they've watched, and porn sex isn't exactly an accurate representation of 'real' sex (at least not in my life). I have no idea that you mean WRT urinary opening vs. vagina.
But anyways, I think that people usually 'pick it up' by kissing, making out and fooling around, etc and realizing what feels good and what makes their partner feel good as far as talking, foreplay, rhythm etc. Learning a female's body and how they react to different things, of course everyone's different. Going from only kissing a girl to having sex with a girl is taking the fast track.
Trimming and being clean never hurts. Practice makes perfect, play safe, and if the girl's experienced she'll be able to help you along the way. Good luck
