A young coconut should make a sloshing sound when shaken and feel heavy for its size. A mature coconut should also feel heavy and contain liquid. Avoid any that have sunken eyes or cracks.
If you're dairy-intolerant, coconut milk and cream are an excellent alternative to cows' milk in some cooked dishes (provided you like its quite strong coconut flavour).
Use a ladle to scoop about a quarter of the mixture ... them flip it over until both sides are golden. Put the egg, flour, coconut and milk into a large bowl and use a whisk to combine them ...