First thing you want to do is remove the decal of course.  Usually you can use a hair dryer to heat up the adhesive and remove the decal all at once....which never works.  So now you have removed the colored part of the decal and have all the adhesive sitting there on your fairing.  Honda Polish is good for removing this stuff, just have to keep it wet and keep rubbing, the crap will start to loosen up and wipe away.  I used a mild household solvent to clean mine off.  Just need to be sure it won't harm your finish, the stuff I used was an oily solvent used to remove stickers and stuff off that nature.

Once you get the backing adhesive cleaned off, give the fairing a wash in some dish detergent and make sure there is nothing left in the area where the decal was.  Wipe dry and check for any lint.  To apply the decal I use a glass of water and alittle dish soap (just a drop or two).  Remove the backing to the decal and dip it into the soapy water.  Apply to the fairing and slide around till you get it where you want it to be.  Then use a squeegee or credit card (be careful of the fairings if you use a Credit card because it could scratch) to remove the water from under the decal.  Have a paper towel handy to wipe up the water on the edges after each pass.  Once it seems to be pretty attached, carefully peel the top layer back, leaving the decal on the fairing.  If you start to pull the top layer away and the decal comes with, try and remove more water from under the decal.  I usually give a few passes with the squeegee once the top layer is removed to make sure all the water is gone.  Done!

One tip is to take pictures before and after from the same angle, so you can compare alignment, especially before you press the decal down.