There are multiple answers to this question as everyone has their own devices that work for them. But the rule of "thumb" that everyone is taught when learning how to shift on cello is to think of it like an anchor. It should keep the frame of your hand together and square while moving through the different positions. With most students who start to learn shifting, the most common issue is intonation or how "in tune" they are after they shift. A good way to practice framework of the hand and intonation is to play an arpeggiation of a bunch of scales while going down each finger.
Ex: If you are playing a C Major arpeggio
- Start in first position on note C on the G string with your typical finger pattern of 4-1-4 (C-E-G)
- Then shift the frame of your hand down a finger so that your third finger is in place of your fourth finger, your first finger is now replaced by your thumb, and the for the last note of the arpeggiated sequence use your third finger for your fourth. 3-thumb-3 (C-E-G)
- Then shift the frame of your hand down again so that your first finger now occupies where your third finger was, then play E with an extended fourth finger on the G string, then note G on the D string with your first finger. 1-4-1 (C-E-G)
- Then shift the frame of your hand one last time so that your thumb is now on note C on the G string, your third finger is on note E also on the G string, and thumb again for note G on the D string. thumb-3-thumb (C-E-G)
- Then repeat the same thing again but going backwards
This exercise will not only help with intonation and framework, but will also exercise your your knowledge of where every note is on the fingerboard. I hope this helps and have fun Practicing!