lux,
A lot has already been said here (including a few people referring to my opinion on the matter), but I'll give some more clarity as to how it stands for me today. These days, I go with whatever avoids the topic of the "paying" part at all.
If we're at a table having drinks and the waiter brings us the check, I don't even look at it. I continue with whatever conversation I'm having with the girl as if the check was never placed next to us. If she looks at the check and begins to take out her card (or cash), I let her do that and don't say anything about me placing money in there unless she does. However, if the check remains there at the time you're ready to pull and she hasn't reached for it yet, I quickly slide my card in and just pay for it. I'm not strapped for money, so a couple of drinks won't hurt me.
The idea is to not make it a topic of conversation. If a girl wants to pay for you, it's best to do it without her asking and with YOU telling her to pay for it. If you bring up the topic, it shows that you place too much value on this aspect of the date, and any repartee you may have with her suddenly has a "crack" in it. You want to avoid placing any emphasis on the money aspect whatsoever.
In the example of a coffee date where there is a cash register and we are both walking up to it, I usually just pay for the drinks without saying anything. In this scenario, it requires more work to talk to her about how the check is going to be split, so I find it easier and more "fluid" to just pay for them without even bringing it up. If a girl is very forward or very interested in you, she may ask you to get a table for the two of you while she grabs the drinks. In this scenario, I understand that she's basically agreed to pay for the drinks, and I let her do that.
In any case, I find that the best case scenarios are the ones where discussion about the money is non-existent. If you can get away with her paying for it because she takes the initiative, then that's great. It means she didn't mind paying in the first place, and you not offering to pay won't affect her opinion of you. However, in scenarios where she takes a passive role and does not take the initiative to pay, it obviously means she at least feels like the check should be split or paid for by you, so convincing her to pay will only put a dent in the mood. In this scenario, I find it best to just pay for the both of you unless you have a very good reason no to do so (i.e. you're visibly strapped for money and she recognizes this).
NOTE: From my description, it may seem like I hardly ever "split" a check with a girl. And if you did make that assumption, then you're probably right. I rarely split the bill with a girl these days because of the fact that I don't like to talk about it -- she either generally pays for the coffee/drinks in full, or I pay for them in full.
- Franco