So basically, I'm 18, I've never had sex, however, I've kissclosed/kissed/made out with this girl a lot of times. I'm taking her out tomorrow and I'm hoping to finally get it in. What are some tips to having sex in the backseat of my car? There should be ample room, the problem I'm having is how do I go from eating dinner, to driving somewhere private, to moving to the back seat, to fucking her?

My plan so far is after dinner, I'll tell her I want to show her this cool spot where we can go and cuddle at. I'll have a blanket in the backseat and say "want to get under the blanket" ... That will get us under the covers, together in the backseat.... Then start making out with her, but then what? Help please! Also, any additional tips appreciated. Thanks.

I usually make sure my zipper is loose first before making out.

Wait until your dick is hard and softly pull her head onto your dick.

Or guide her hand onto your bulge while making out. She'll get the picture

In a dark, small car getting under the covers sounds inconvenient. I don't know whether you've ever tried it, but cars are very uncomfortable when you're trying to have sex and not being able to see anything gets you stuck in the covers. It's not practical and the car wasn't comfortable in the first place, so covers are not really in place. Just turn the heating way up. When you're in a car, seriously, don't try any of the missionary positions. Your feet will bump the interior which breaks up the tension.
I suggest the following. Start making out in the front seat. This is uncomfortable for your neck, so say you'll move to the back so you can hold her. In the back seat, pull her onto your lap and kiss/finger her in that position. Then get her to grind on you in that same position. You can switch to fucking with her on top easily in this position. Doggystyle is also manageable in a car but when you've never had sex with her, she may want something more intimate first.
You said you wanted to eat her pussy first. I'm not sure how big your car is, but in general I think that whatever positions are very uncomfortable you should avoid because it's just bad for the SPAM to be clumsy.

Appreciate this advice. And yes, I have cloth material. If some kind of secretion gets on it, oh well, shit happens.

The car isn't the most comfortable place ever, however, missionary is actually really easy. Slide the front seats all the way forward once you get out. Lay her on her back on the drivers side kind of angled where her head is resting against the rear drivers side door and the back seat. You have one foot on the ground, kind of underneath the passengers seat and one knee up on the back seat and you're golden lol I've had to do this several times when I had nowhere else to go. It's not as comfortable as a mattress but you've gotta make due with what you got. Hopefully you don't have cloth interior...........