Some of these are mentioned in the chapter on Things needed (9).

In a small library which is always to be small it is not necessary to follow all the rules laid down in these books.

It is much better, however, to do all the work, even in a very small library, according to the most approved methods.

So to do brings you in touch with your fellows and gives you the comfort which comes from the consciousness of work well done, even if the amount of the work be small.
In writing the subject-headings difficulties will soon arise unless you follow certain general rules and are careful also to be consistent in your work.

For instance, at intervals during a few months you add to the library books on horses, cows, sheep, goats, camels, and pigs; some dealing with one animal, some with two or more.