Here is a good read.

It is easy, just take a male plant from one strain and a female
from the other. Say Big Bud and Skunk. The result will be BIG BUD
X Skunk, but there will be differences in the pack. Some of the plants
will lean more in the BIG BUD direction and some in the Skunk
direction. Some variations that where not present in the parents may
also appear (if the parents where not both IBL). If you want to
concentrate on creating more seeds so that they ONLY go in one
direction (creating uniform plants).

The Cannabis Grow Bible has a wealth of information in it!:thumbsup: