I am a few years out of graduate school but I am more than happy to share a method that worked for me in hopes it might help someone else out. I'm going to type a bunch because it took a lot of thought processes to keep myself on track and to not screw these situations up. I am no sex God or anything, I was just your regular guy trying to see some boobies.
When I was hanging out with my good female friends I would start rubbing their backs while watching television or if they made a comment that they were sore, etc. I would make sure I did a REALLY good job, asking them what felt best and where to hit the tough spots and once I gained their confidence I could put my hands to their back from under their shirt. As time went on I would eventually get them to go lay on their stomach in the bed. I was always very casual about that, saying "come lay on your stomach in the bed so I can do a better job." By first putting the image in their head that they were going to be laying on their stomach getting a massage, they are focusing on that rather than thinking about how you are getting them into the bed!
Now that they were in the bed I could start rubbing their back. But wait, all that freedom of movement I got from rubbing their back under their shirt when they were sitting erect

is gone. I would start to make it seem tough to rub them over their shirt, making it feel gritty as their shirt rubbed against them or act like I was not able to get my hands far under their shirt since they are laying on most of it. From here, it gets easy. A simple, "you're wearing a bra, right? Let me slide your shirt off so I can get at the top of your back" (Note: this one got me into trouble once, “slide” rather than “take”). Once again you are making them comfortable by reminding them they are wearing a bra so it is okay to continue the massage rather than think about how you now have them half-naked! Then I would start rubbing in sweeping motions across their back but now that bra strap is catching hell! "Mind if I unhook this, it is getting in the way?"

. At some point boobies will work their way into the picture but it is, of course, tricky. I had luck when starting to rub their legs as well, some would quickly dump the unhooked bra to get those pants off so you could rub their legs.
In one case, while I had a girlfriend, a freshman (virgin) would let me unhook the bra but would always re-hook it to remove her pants, etc. This was frustrating and went on for quite a while but during one massage I had the thought to rub her legs, lightly on her stomach and sides and to the top part of her shoulders. Then I had her put her head in my lap so I could rub her head. Done correctly it simply puts them comatose and in this particular situation I finally gave up and innocently said, "Can I take off your bra so I have something to look at while I rub your head?” (“take” did work this time). I think the bra flew so far it hit the other wall across the room. After a couple of months of this the bra was off and boobies were flapping before she even got in the bed. For those interested, she was your “girl next door” with medium height, brown hair, a cute face and medium breasts. The breasts were big enough to sag and the areolas were dark and on the larger side. Her nipples were flat and did not get erect (that I saw).
In the rare occasions it got to that point, I would play it safe though and rub the breasts rather than fondle them, no sense screwing up a good thing when there really isn’t much different between the two methods!
I had one girl, she was rather tall with freckles on her chest, face and back. She had no problem dropping the clothes in order to get a massage. She was fully-built, nothing flabby, just solid I guess you could say. She was not very proportional up top as they were smaller and very erect and stood away from her body, they were different than I had seen before in person so I really enjoyed them. When she was laying on her stomach I would rub her all over and when rubbing her ass I would do it in a way so I could get a great view of everything. When she would turn over so I could do her legs I loved seeing her tits pointing so far up (she had pale tits with medium sized areolas and flat nipples). Of course I got to them eventually. After a few meetings she started giving me a naked massage after she got hers but I also got a happy ending! I unfortunately didn't live close by so this only happened a few times.
Most importantly, if there was anything that I learned in college, it is that it NEVER hurts to ask! (especially if it is in a respectful and humble manner) I had far more sexual experiences because I simply asked politely.