Important lectures of a new breeder:

About selective breeding:
http://www.hiiret.fi/eng/breeding/?pg=3

Mouse varieties:
http://www.hiiret.fi/eng/breeding/?pg=4

About "culling", i.e. litter reduction
http://www.hiiret.fi/eng/breeding/?pg=2&sub=7

What should a "show" mouse look like?
https://www.afrma.org/stdsmse.htm

Head and tail shape:
https://www.afrma.org/brdstf_msehdbuttcoat.htm

Ears:
http://www.afrma.org/brdstf_earsetmice.htm

General about the type:
https://www.afrma.org/type.htm
https://www.afrma.org/mk-type.htm

Outcrossing, Line Breeding, Inbreeding:
http://www.afrma.org/breeding-inoutline.htm