What a lot of women aren't aware of, is that cup sizes change when back sizes do. When moving up a back size, you'll have to move down a cup. For example, if you find that a 34C is too big on the back, you're best to try a 32D, and vice versa. To ensure the bra fits you properly, I recommend leaning forward to make sure that you're completely in the cups, and always adjust the shoulder straps to ensure better support and lift. Always fit the bra in the loosest fastening - this way if the bra stretches with wear and washing, it can be tightened to give the same fit.
When looking to see if a bra fits correctly, I'll make sure that the breast isn't spilling over or leaving a gap, and that no puckering occurs on the cup. I'll also check that nothing is spilling over the sides near the underarms, and that the bra doesn't ride up at the front or back. I'll check that the customer feels supported, and that I can comfortably insert 2 fingers under the fastening at the back without too much pull.
Also being October, it's no secret that it's breast cancer awareness month. Although this set isn't exactly pink, it's always important to get the message across. I've come across a great website that encourages people to find the signs of cancer early and therefore have a better chance at beating it. KnowYourLemons.com is an insight into how breast cancer looks, feels, and is found.