You really need to go on the main site and read the articles there, I can't think off hand what article would benefit you the most, but answering those questions is basically what this site is all about.
When you say disco I assume you mean basically bars and nightclubs, I would refer to this as "nightgame"... if you are already getting grinds and conversations with girls you're 90% of the way there, what you need to do is focus on moving girls.
What happens is that you meet them, you grind with them a bit and the sexual tension builds, but then starts to die. So after a while she figures out you're not gonna do anything and turns back to her friends. This has happened to me quite a bit.
So when the tension is at its peak (after grinding on her for a few minutes and establishing some sexual eye contact perhaps) then you say "hey lets go grab a drink / cigarette / whatever" or perhaps "it's really hot here, lets go sit down over there and talk a moment" et cetera.
It doesn't really matter what excuse you provide, or if you're a strong confident dominant mofo just grab her hand and move her somewhere ("taken compliance"), or as an in-between approach, order her to do something without giving a reason ("unjustified compliance").
The point is after having moved somewhere with you (even if its only a few metres away from her friends on the dancefloor) she is much more committed to the interaction ("investment"), and as a side effect she's further away from interfering, distracting, cockblocking friends... preferably out of their sight line.
I wouldn't try to pull her to the toilets straightaway, that would be like going from 0 to 100 km/h, you need to advance your seduction more gradually... once you get her isolated try to find out a bit about her and what makes her tick ("deep dive")... look, if she's thirsty and ready, go for it ("skipping steps") but that's unlikely, most likely you'll have to follow a process to get her ready. The end of this process would be saying something like "I'm hungry, let's get out of here" and taking her home with you ("plausible deniability"). You can also go for a makeout in a quiet part of the club, although she'll probably lose interest in you after that.
-Ray
