When using a pearlised enamel... always apply the base coat and three thin layers of enamel.
When applying a none pearlised enamel.. apply the base coat and two thin layers of colour and a top coat.
If apply a french polish... always apply a ridge filler first and allow to dry, then the base coat, the white tip and then a top coat.
To prolong your enamel longer then apply a clear coat of enamel the next day and every day.. this will help to stop chipping.