Many times you can avoid drilling a hole for finish nails in thin molding materials using this trick. Use your hammer to gently tap down and dull the sharp point on the nail. Don't mash it flat, just dull it about 30%. As often as not you will find the nail will penetrate the trim without splitting it....when I tried to put my first finishing nail vertically into the new base cap, it was about to split (so I pulled it out and pre-drilled the hole).
It seems counter-intuitive, but believe me it works. A sharp point pries the wood fibers apart much like a wedge, making it split along the grain. A more dull tip breaks the fibers and allows the nail to punch through without wedging the grain apart.
As a side note, the wedge action is actually beneficial to a nail's holding power. A nail that is "wedging" through the wood holds better than one "punching" a passage into it with a dull nail. The wedged wood fibers tend to want to close back up and pinch the nail to keep if from pulling out easily. If all nails were dull, the hole they punch into the wood has less holding power, as the fibers are pushed aside creating a bit more of a channel. I also use this technique when hammering larger nails into 2x4's near the edge, or when toe-nailing near the end of a 2x4.