One of the most common mistakes one should avoid when applying nail decals is applying nail decals on wet nails. Make sure the hands are dry before applying the decals. Skipping the base coat, not trimming the decals properly to fit the size and shape of the nails before applying them, not smoothing out air bubbles while applying the decals, not using a topcoat after the decal has completely dried and using too much water during the process are some other mistakes that one must avoid to achieve a flawless finish when applying nail decals.