If you use the Olay body wash with shimmery stuff built in (ribbons or whatever), don't use it that day. It showed up as sparkles on the film and I had to have extra filming because of it.
Also, since many facilities don't give you much of a choice as to whether the mammogram is scheduled around your period or not, I take some ibuprofen beforehand to lessen the pain.
I'm not so sure that it's more painful if you're blessed (or cursed) with excessive "cuppage", but it's more a matter of whether that tissue is dense. The denser you are, the more they have to compress is to get a good image.
I'm assuming this is your first, so it's a baseline scan. From then on, the techs will have something to compare when you go in for others. Try to relax....it is nerve-wracking but it's better to face a little squeeze now than the alternative.