I think this is the kind of thing that she will make obvious or be willing to initiate if that's what she wants. I was mindful of this with my boyfriend because I knew he was too shy to actually ask, so I asked him if we could have sex when I was ready (a month into dating).

If you're in a relationship, I would strongly recommend talking about sex in a nonsexual setting (i.e., not when you're making out) so that you can hear each other's thoughts, make sure she's ready, go over birth control/condom issues, and discuss each other's fantasies and talk about new things you might want to explore. Talking about sex with your partner is really helpful during any stage of a relationship because it allows you to keep sex fun and interesting for both of you and make sure that everyone's satisfied with what's going on.

If you're talking about just a hookup, then it's a little bit trickier. I still think that she will make it clear if she wants to go further. Girls can be pretty sexually agressive, so I think a girl who wants to have sex with you will do things like start unbuttoning your pants and ask if you have a condom. If she doesn't, you don't want to press her into anything, but you can gauge her feelings by slowing incorporating more intimate things - rubbing her breasts, taking off her shirt, unbuttoning her jeans. If she doesn't want you to do these things, she will tell you to stop. If she feels like its going too fast, slow it down a little and go back to the last thing you were doing. Maybe she's OK with oral but not intercourse, maybe she wants to do handjobs, maybe having her shirt off is as far as she wants to go.

I think the most natural way to figure this stuff out is by the trial-and-error method, as given above. If she pushes your hand away from her pants, then she wants to keep them on. But, talking to her is the other way to figure it out. You can just ask her, and yes, it may be a little awkward. However, having sex with strangers/acquaintances is sort of awkward by nature, at least in my opinion. I'm sure it's nothing she hasn't heard before, so you don't need to be embarrassed. Just a simple, "How far do you want to go?" or "Just so you know, I have a condom if you want to have sex," will do.

Good luck, and I hope this was helpful!

Please do a forum search using my name and the key words "implied consent" or "boundaries" for the answer.