How do I propose or at least making out with a girl without being to forward?

I know this girl and we hang out almost everyday. A lot of times alone. The first time we hung out i blatantly asked her if she would like to makeout and she said no but we have hung out a lot since then and she has given major signs so im guessing that was just to soon. For example last night we were at this party and we were smoking pot out in her car and having a great time. She then said she had to leave so everyone except for me went inside. Then we left the party and drove to an empty parking lot down the road and just talked more but I had no idea how to propose making out without being weird and i don't want to be to forward either like pounce on her or something.