It's interesting to hear about clinics that have a morning and an evening shift. I guess I must work at a relatively small place, though we have three doctors. There is always at least one tech who is there all day (7:15 to 6), most days more than one. Usually there are only two of us who have a half day (one in the morning, one in the afternoon) and the others fill us in on what's been going on.
We were open 7:15 to 7PM and rarely ever left before 8:30PM at night.
Usually you would work either 7:15-5PM or 9:30-close (whenever that might be). Depending upon the schedule, other peoples' schedules, time off requests, number of staff, etc... you could end up with 3 12 hour shifts (working open to close) or you could end up with one 12 hour shift or two. They tried to keep us at 4, 10 hour shifts each week. Though things would get shifted around as needed. So, the "Night" techs would really have been there all day. However, we did have some night techs that were in school and so their shifts didn't start until 1 or 2PM. So they would need to be filled in. We would also officially "hand off" patients. This way there was no question as to who was to be watching over a particular pet. Granted most everyone knew a little something about each patient when we did the afternoon/evening "hand off" it was a way to say "ok, X technician is taking care of y and z patient". It was also a way to be sure that the tech did know what they needed to do for the rest of that day.
I always made it a habit for when I first arrived at the clinic to do a quick glance over of all patients that were on the schedule. I would read history, check vaccine status, etc. I would know what times of the day were looking to be "slow" times and what times we might be "busy". I also knew which pets to expect around what times. I would have a general idea of every pets' history and for the pets I would check in, I would read their histories more in depth and I always read them before going into the exam room. But, I did a lot of supervisor type of things... such as organizing employee lunches for the day. This required quite a bit of balance. Each employee would get a 30 minute or hour lunch break depending upon the length of their shift. I had to know which employees were working AM shift, which were PM shift, which had 8 hour shifts, 10 hour shifts or 12 hour shifts. I had to know what was going on with the schedule. I had to know who was going to be the surgery tech and where they were at with surgeries. If we only had one receptionist for the day, I would have to fit her into tech lunches and have a tech cover reception. I had to have a general idea of what each tech was doing, where they were, etc. I would have to keep a running tab in my mind of who is going to lunch 1st, 2nd, etc (AM techs get lunch first, followed by 12 hour shift techs, followed by PM techs) and if I can overlap lunches (send one person, 30 minutes later, send another, which was usually best). It became habit for me to basically have an appointment schedule memorized, as well as type of appointment (vaccine vs. work-up), and knowing what all the techs were doing as well as what the vet was thinking/planning treatment-wise for each pet they were dealing with.