The way that works for most Pokemon, including all three of these, is to use role play. This should reveal the target's ability. Additionally, many Pokemons' abilities can be determined using other methods.
Cubone's hidden ability is battle armor, so a guaranteed critical hit move like storm throw will land critical hits as long as it doesn't have battle armor. Use storm throw against wild Cubones, and the hidden ability ones will not take critical hits.
Minccino's hidden ability is skill link, which forces tail slap to hit 5 times. If it uses tail slap, and tail slap hits less than 5 times, then the Minccino doesn't have its hidden ability.
Fletchling's hidden ability is not big pecks, so its physical defense can be lowered. If you use leer or tail whip on a Fletchling, and it works, then the Fletchling has its hidden ability.