1. I don't know if it's customary, but it's certainly nice. And waaaay better than that stupid "Playing it cool" idiocy.

2. No, not totally weird, depending on the situation. I mean, if she doesn't *want* to go out with you again, and you're dragging her around by her hair, then it's probably totally weird. If she's legally competent to give consent, however, and she does so, then I'd tend to assume she's ok with it. Unless she's one of those people who say "yes" when they mean "no" and will get all resentful and crap, but then that's totally her issue and you really don't want to date one of those people anyway, because she'll be all "Why can't you read my mind?!?!" and you'll be all "Because I'm not a mindreader!" and she'll be all "Lack of supernatural abilities is no excuse for not having supernatural abilities!" and you'll be all "Whatever!" and it'll be a disaster, you know?

3. I think I generally held off asking until there was sex involved.

1. it's not customary, but nice I think, especially in the age of email. I'm pretty much an email/im person so if you called I might think it was a little odd (why didn't you email?) but not really weird at all. Basically if someone is into you, they will think it's nice and I don't think it's likely to send someone into "not into you" territory if they're on the fence.

2. if both people are into it, it's great and not weird at all. If you're sort of wondering whether to ask 'em out a second night in a row, I'd say maybe not unless you had a really strong feeling they were into that

3. I'd ask if it mattered to me or at the point it mattered. I'm pretty much with occhiblu here, if I were going to sleep with someone and didn't know their status, I might want to know, but whether that knowledge might affect my behavior, who knows... The guy I'm dating asked me pretty early on, and when I got done laughing about it ("me? dating someone? oh that's hilarious...") I thought it was sort of sweet and, in my opinion, nice to get that conversation over with early since our feelings jibed on the matter. THAT said, I was certain the reason we were having that conversation early was some sort of indicator that we were going to have an "I've got herpes" discussion (it wasn't) which has become a total funny after the fact joke now.

1. If you want to talk to her anyway.
2. Not if you both had fun.
3. It's good to let her know your interests if it's not clear. Does she think you're just friends?

My subjective take:
1) I'm not a guy, but I have received such calls. I always appreciate the gesture when I do get them. Even if I did not have a great time on the date, that call makes me think the guy is pretty nice. However, I always feel extremely awkward on the phone, so personally, I like those calls to be close-ended. You know, not a call to chat, but a call to say you had a nice time and am I free for a drink on Wednesday.

2) I don't think it's weird. I've gone on dates on Friday and been asked back out for Saturday. I, however, have a personal "rule" against it for reasons which have entirely to do with my own idiocy in dating. So. I don't think it's per se weird, but it can up the ante too soon. So like Jessamyn says, without a strong signal to ask for a back-to-back date, I wouldn't recommend it. Instead, call the next day, say you had fun and see if you can get together next weekend.

3) I am finding it really difficult to express my opinion on #3. If you think she's hoping to cheat on her boyfriend with you, you should ask right away. If you think she's dating someone and just wants to hang out with you as friends, you should ask right away. If you think she's casually dating more than one person, I would hold off until you are attached enough that you want her to know you have no interest in dating anyone else casually. Like occhiblu says, for many people that's after the sex / right before the first sex.

I definitely can't give advice on dating, but I can give advice on one single thing - if you find a person with whom you have a really overwhelming mutual attraction that is not just sexual (I know that sometimes it can be difficult to tell) - you might be able to dump any kind of rules or etiquette (or even common sense) and just go with what you feel straight out.

V. and I must have broken every single rule of dating and relationships and discarded every bit of conventional wisdom that is meant to keep one from making really stupid mistakes... and for us, that was the best thing we could do. I would never suggest this to someone who wasn't fully adult, or someone who didn't have enough experience to tell sexual urge from real emotional, mental and physical rapport. But if it seem you are feeling something like that, and it feels like she is feeling something like that, I'd call the next day, and have back-to-back dates, and ask about boyfriends.

If it was just really nice, and has hints of promise, I'd call the next day, wait for her to mention getting together again and work the conversation so that if you do end up going out again right away that it comes by way of both of you sort of hitting on the idea that this would be cool/fun, and I wouldn't ask about boyfriends.

Hiya, here's some exotic data points from someone who doesn't do the dating thing (mating rituals in Scandinavia are different, so I've never actually been on a date!).

Calling after a great night out is the thing to do. Else I might not know that you also thought it was a great night, and by the time you call next weekend, I've made other plans and secretly resent you for not calling. Unless I call you first just to check where we stand on that "great night out". In non dating worlds, being very clear about intentions is key so a non-call is equal to a never calling you again.

If I go out with a guy (note, going out with a guy is not automatically a date - we pay for our own drinks, meals and can go home when we please without an escort, though someone walking you home is sweet) and we end up having a great time and he asks "so hey, there's a thing tomorrow wanna go?" I'd be totally up for it, nothing weird at all. In fact, in my non dating career meeting on Friday and hanging out also on Saturday is the norm, unless you're both really tired in which case offer movie-night. That's why you have two days in the weekend.

Most commonly, when you are a non-dating scandinavian, you won't be seeing anyone else. You're single, and seeing one guy on the weekend might turn you from single to non-single right then and there. There is no hanging out with ten guys in shifts and leaving all possibilities open, either you are interested in some bed gymnastics with them, or you are not. It's very rare that girls see more than one guy at a time, as "dating" isn't official until after sex (or at the very least second base - though it may take a few weeks before you both call each other boyfriend and girlfriend), and seeing more than one for that probably means you're polyamorous which is rather unusual. (Not that it doesn't happen.)

1. Yes, call her if you liked her and want to see her again. It is good to establish interest early and make her feel secure. A little mystery is nice, but not a mystery about whether you had fun. If you aren't ready to make another date yet, you can email or text her something really quick, like "I had fun!"
For me, that's really all it takes to go from the guy who was a fun date and I hope he calls to a guy with boyfriend potential.
I think most women like responsive and reliable guys who call when they're supposed to and tell you how they feel. It's good to establish that you are that guy early on.

2. I don't normally see people that often when I am first dating them, but that doesn't mean much at all. Everyone goes at a different pace and there are a lot of other factors (like: is there something coming up that you are both interested in? that might merit a 2 date weekend) that could change my mind or make it seem more normal.
Other people have 0-60 in 10 seconds style relationships where they meet, decide they like each other, and then spend large chucks of time together. I set up a couple whose first date lasted 3 days. It depends on what kind of person you are or she is.
She'll say no if she doesn't want to see you again so soon, or you will hear some hesitation in her voice. I'd say to be safe, wait a few days before the next date, but that's just a reflection of me.

3. Don't bring it up. She will sort her own crap out in her own tome. It will soon become clear if you are going down the path of exclusivity, and you can talk about it then. Or you may never have to talk about it-- many times it is just silently accepted that you won't be seeing other people. This happens at a certain stage of intimacy, which is probably not by the second date. It could be around sex-time, or if you want to take her to some event as your date, or if someone else asks you out and the issue comes to a head.