According to the same book I've been discussing for the last three entries (Rabbit Production), certain traits have certain degrees of heritability. On pg. 326 the authors say that,
"In general, traits related to fertility and disease resistance are lowly heritable (<15>40 percent)".
Improving traits that are lowly heritable is accomplished by establishing culling levels rather than by direct selection. In other words, to breed better mothers or does who conceive more readily with fewer misses, simply cull out does who do not take care of their babies or continually fail to conceive.
Improving traits that are moderately to highly heritable, on the other hand, is best achieved through Direct Selection. For example, if you are trying to improve the density on your FAs (a moderately heritable trait), then you should select and breed only those rabbits who display superior wool/density, and gradually your herd will improve in that area.
A place where much more specific selection must take place revolves around the color genetics of a herd. In this case, rabbits are born with specific genotypes (genetic codes), and when we breed them together those codes are combined in various ways in the offspring. Selective culling to get rid of certain color traits will not work in this instance, because simply getting rid of a baby who is a Chinchilla will not eradicate the Chinchilla gene in the parents or your herd. In order to completely get rid of certain genes in an offspring they must be selectively and intentionally bred out. Even Direct Selection will not eliminate undesirables, because choosing to breed only those rabbits who are NOT Chinchilla won't work. The gene can be carried even though the rabbit does not express it. Genes may lurk for generations until specific breeding combinations bring them out, and this is especially obvious in the area of color .
If I am looking to eliminate Chin from my litters completely (just as an example), the only way to do it would be to breed a Chin Carrier to a REW, and the resulting babies will then be devoid of 'chd' because of the contribution of a small c from the white parent. In color genetics, rules of selection apply that do not come into play with other traits.
There are many ways to select for and against different traits in a rabbit herd. Although methods may vary, the most important thing to remember is that breeders need to select clear goals for their herds and then stick to them! Circumstances change and goals alter whenever we learn something new, but as long as you choose your methods of selection and stand by them for the long term, your herd will progress. I once asked a very well known rabbit breeder what she considered the most important factor in developing a winning herd and she said, "Consistency". Understanding how trait selection works goes a long way toward increasing the quality of your herd, and is well worth the effort and research:).