Pic your best Male, and your best Female, you can do an open pollinated, or this method
https://www.rollitup.org/advanced-marijuana-cultivation/20319-seed-production-tutorial.html
After that those feed will be F1, save the pollen from the first batch, and just keep using that after each grow, fo after you grow the F1's out, pollinate the pheno you want or whatever. That will be F2, and so on. you have to do it at least to the F4 stage to be stable
im doing this on my next grow
or starting, most people start with an IBL,
What is an F1, F2, and IBL?
An IBL (inbred line) is a genetically homogeneous strain that grows uniformly from seed.
Basically, this s when you start with one strain, like WW with WW, when you take two different strains, its a mix of a bunch of characteristics
A hybrid is a strain made up of two genetically unlike parents, IBL or hybrid.
When you cross two different IBL strains for the FIRST time, it is called the F1 generation. When you cross two of the same F1 hybrid (inbreed), it is called the F2 generation.
The process of selective inbreeding must continue at least until the F4 to stabilize the recurrently selected traits. When you cross two specimens of an IBL variety, you get more of the same, because an IBL is homozygous, or true breeding for particular traits.