Punnett Squares

Let's take a square, and let's split it into quadrants. Let's use eye colour for this example, and put two brown uppercase B's in the top left and right, and then put an uppercase B, and a blue lowercase b, in the bottom two squares.

Since we put them as uppercase the two uppercase B's are the more dominant trait, and the small blue lowercase b's are the recessive trait.

So the chances that a child between these parents (uppercase b's) has a 50% chance to have a child that has brown eyes, but a 0% for a child to have blue eyes, keep in mind the uppercase B's are Genotypes, while the lowercase blue b's are Phenotypes.

Now, let's cross two parent flowers, one red, and one white, and when you combine the red and white alleles, you get... Pink. This is blending, it's a mixture of the two colours, and the traits that both parent flowers have, and they are both incompletely dominant, so they blend instead of having one or the other. 

Now let's try blood types, let's pick three for this example: A, B and O blood types, Let's say one parent has an AB blood type, meaning they have both A and B types, and they do not blend as they are both dominant alleles. And are co-dominant

Let's say another parent has an A blood type, and their phenotype is an A blood type, and their genotype is an O blood type. This is interesting about blood types as O is recessive, while both A and B blood types are co-dominant.

All the combinations are as follows: AA which means that you have only A blood alleles, AB meaning you have both A and B alleles and are co-dominant,
AO and BO blood types are still going to be A blood types because the O allele is recessive. So there's roughly a 50% chance to get a A blood type.
So if you want yourself to be a O blood type, both of your parents must carry a O blood type.