1) Depends on where the flat is; most college girls are not partying on campus over the weekends so if there are any hot-spots near your private flat then I'd recommend going to those places and following the common logistics that GC lays out.
2) If you're out with a girl and want to go back to her place then you simply figure out what her logistics are ahead of time: "Which dorm are you in?" or "What part of town are you in?" then you follow up with "Awesome. What's your roommate situation?" and then she'll go into details. Keep in mind that if a girl wants to sleep with you she will put in some effort to make it happen (without telling you that blatantly, of course) so, if she has a roommate then she likely knows her schedule or will text her and let her know she might be bringing company over and the roommate will leave, etc.
Following up with that, if you're on a date and her logistics check out then you roll with something like "I'm really enjoying spending time with you, how about we get out of here? Your place is a lot closer than mine, in XYZ. How about we relax and unwind for a bit? We can hang out/ talk more/ throw on a movie/etc."
3) Provided she has a roommate and for some reason both her place AND yours are unavailable then you bounce to a different location (like a park for a walk, etc.) and escalate lightly, provided the two of you are vibing well, and then you set up a plan with better logistics for the second date. So, you end the first date on a high note despite not being able to go to her or your place and then, in the near future, the two of you can work out a time or plan when either the roommate is gone/busy/etc. or you two have a date somewhere closer to your flat.
One last thing, after you sleep with a girl and she figures out that you have a private flat then it gets a hell of a lot easier to keep "on-campus" girls around because they know they can go to your place, even if it's a bit of a drive, etc.
-Richard
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