On cello and double bass, the player pulls the bow to the right, away from the left elbow.
Down-bows, which begin near the frog, are therefore often used to play the downbeat (strong beat) within musical phrases.
Notes that begin loudly and diminuendo are ideally down-bowed — from frog to tip — allowing pressure on the string to decrease naturally.
Up-bows, which begin near the tip, are therefore often used to play the upbeats (weaker beats) within a musical phrase.
Notes that begin quietly and crescendo are also ideally up-bowed — from tip to frog — allowing pressure on the string to increase naturally.