Should I always use the printed bowings? The answer may vary depending on the situation.

When playing in an orchestra it is acceptable practice to use the printed bowings. However, the printed bowings maybe superseded by the principal player of the section, the concert master, or the conductor. The norm is that all of the players are bowing the same direction at the same time. The same direction bows create visual unity as well as a more uniform sound.

If you are the only player, the answer to the bowing question is a lot more relaxed. The purpose is to express the music in the best way. So the printed bowing becomes a guide. For example, if you are performing with a choir, and are asked to play more loudly or softly, changing the bowings is an efficient way to produce the sound that has been requested.

Sometimes you may be asked to play from a piano part. The phrase marks in piano music do not always work well as string bowings. Judgement is required to rebow the music to execute the phrase.

Other times you may be handed music that has no bowings at all. Once again experience is needed to determine the best course of action.

So as a general rule, when playing in a group, bow like the group. When playing alone, bow to make music.