How to know that one character is dominant and other is recessive . Is there a way to identify them?

Dear Student

Dominant trait is the phenotype which is expressed when the genome is heterozygous. It has dominance over the recessive trait. While the recessive trait is expressed only when the alleles for the character are in homozygous condition.

A test cross is usually done to identify dominant and recessive traits.

Also, 

Dominant traits are those traits which are expressed even in the presence of one copy of an allele for a particular trait in the gene. For example: Yy shows the dominant trait for yellow color of seed. Seed is yellow even when single copy of dominant allele i.e. Y is present. 

Recessive traits are those that are expressed only when two copies of an allele are present in the gene. For example: yy shows the recessive trait for green colour of the seed. It is expressed only when both the alleles are recessive i.e. y.

Regards