How I apply decals:
1. Glosscote the area the decal is to go. I usually glosscote the entire model to serve as a protective coat. This is important; not only does it improve decal adhesion, it helps prevent air from getting under the decal and causing the clear areas from clouding (called "frosting" by hobbyists).
2. Soak the decal for the recommended time. I usually dip the decal in water for 10 sec, then let it sit on my desk until the required time is up. Some decals don't list a time, so I start testing at around 45sec. Some may take longer.
3. There is no need to float the decal off the backing paper. Instead, place the decal with the backing paper still on at around the area the decal is to be applied. Using a brush, gently slide the decal off the paper and into the correct position. You might need to use a little water to lubricate the decal so it will move more easily without tearing. Some people like to use Microset under the decal. I do not. YMMV.
4. Blot away the water with a tissue. I usually touch a corner near the decal to suck up the excess water, then gently blot from one corner to another.
5. Use a decal solvent like Microsol or Solvaset. This performs two functions: it softens the decal to better conform to details, curves, etc. as well as snuggle the decal down and lessen the edges of the carrier film. After drying if you notice any air bubbles, stab them with the tip of a hobby knife and reapply solvent. DO NOT handle the model around the decalled area until fully dried.
6. Once you are satisfied with your decal job, apply another coat of glosscote to seal in the decal and further hide the carrier film edges. With high quality silk screened decals, this will make the decal look painted on. Lithographed decals usually have heavier carrier film, so might need multiple coats of solvent to get them to snuggle down and eliminate the carrier film. Usually it is best to use an acrylic glosscote at this stage (skipping a step and using a dullcote at this stage is not recommended -- it may help highlight the carrier film edges instead).
Disclaimer: I have been a plastic modeler for the last 30 years.
Damon.