All this means is that the random selection of one trait will not determine the random selection of another. (This of course assumes that the genes are on separate chromosomes.) In other words, the genes for your eyes are transmitted independently of the genes for your height. Your kids could be tall with brown eyes. Or, your kids could be tall with blue eyes. The traits, or the alleles, assort independently of one another. See the dihybrid example below. As you can see, there are 4 possible outcomes. One letter does not affect the selection of the other.
The following phrase may also help you determine the gametes of a dihybrid:
BIG à BIG
BIG à small
small à BIG
small à small