It helps to put a liquid layer on the model just prior to placing the decal.
I used get a little saliva on my finger, wipe it on where the decal is to go...that helped a lot! Then I discovered micro-set, which also worked. These days, I brush on a little "Future", place the decal (roughly), a quick dab with a paper towel, then move the decal into it's final resting place...then, with a little bit of pressure, kind of roll the paper towel over the decal, pressing out and soaking up the excess.