When dealing with FPG's decals I;
Paint the mini, cut the decal, apply a some Testor's Decal Set (this stuff basically cleans any oil that may have been deposited from my fingers. Some people use a white vinegar and water mix). Once the decal is where I want it, I apply some Micro Sol. This stuff makes the decal soft, and allows you to push it down into the panel lines, and helps a decal adhere to curved surfaces. Then I seal with acrylic and go over that with Testor's Dullcoat.
Technically you could get away without the Decal Set and/or the Micro Sol (or their equivalents), but they do make that little bit of difference and every little bit helps.
When cutting the decal, you need to know what kind of paper it is on. Basically there are two type: Clear and White. When cutting clear decals, you really don't have to be too careful. Any excess will be pretty much transparent. When cutting white, you have to cut every curve and edge close... The advantage of white decal paper is that the colors of the decal are more vibrant, with Clear, the background color bleeds through... To the best of my knowledge, the majority of FPG's stuff is on clear, and maybe only decals that are in some part suppose to be white (like certain of their numbers) will be on white.
As for the Wolf's Dragoons decals coming out a perfect oval, they do not pre-cut the decals, so that was all you. But since the decals are on clear, you could have cut them as a square, and the rest would just disappear against your paint job.
Caz