*Raises hand* Recent grad here.
Patient records are legal documents, and even if you are seeing Aunt Bettie's rare lizard (and don't normally see lizards) you better darn well document it. (Particularly if the lizard dies on the way home and she sues, oi)
A new patient or current patient visit always starts with a good history and a physical exam (PE) which are written down on two sheets or the same one. Even if you saw the pet a week ago, you want to know what has changed, how the animal has been doing in that week, did they get their meds, etc. (I can give you a better list of history questions if you like).
If you are doing more than 'wellness' (PE, yearly or puppy shots, deworming, and other basics) you'll want to provide an estimate (radiograph cost, bloodwork, et al). If the animal has to undergo anesthesia and or surgery (can have anesthesia w/o surgery for various reasons) you'll want a release that says there are risks involved and detailing that.
Shal talked about daily flow sheets: Little notes for hourly walk bys, when they got their meds, their twice daily TPRs (temp, pulse, and respiration. and also mucus membranes and CRT capillary refill time). If the horse was sicker, they got a more intense flow sheet and more done hourly (or every 30 minutes).
Client communication has to go there, daily SOAPs, a prescription log, etc. Case summaries. Operative reports.
Separate from the patient files, all hospitals/doctors have to keep a prescription drug log for all regulated medicine (morphine for example) and if any is spilled on the floor (did that last week) you have to document it. If you don't, huge fines +/- loss of license.
So yeah, paperwork becomes a big deal legally. I was told many times: Patient records are legal documents.
To answer your last question: Pretty much all treatment is recorded. If we are drumming on a big dog's chest to get the plegm out (on top of inhalants and other meds), we might not worry about that little detail b/c you can see from other stuff that we are treating the dog thoroughly. But if it gets meds, it's recorded. When we take the TPR, we write it down. We give them fluids, we write it down (what they got the last hour, over a running total- so it takes 1 square on the flow sheet, but the record is there. I don't know of anyone that writes out 'and we will start the patient on Norm-R at a rate of blah blah until...' It's just there, on the flow sheet, with the start time and stop time visible, along with changes. See?). We are going to do an MRI tomorrow? We write that out on the SOAP since the P is for 'Plan', and if they are recovering in ICU b/c they got contrast, we can mention that or throw the ICU flow sheet in the record (it's going there regardless)
Am I making any sense? LOL.
ETA: The level of detail in the record depends on the practice and also on how sick the patient is, and also the doctor/tech/student, and also how busy they are that day.
Avians/exotics usually have special forms since stuff is different for them, but a small animal practice that doesn't see a lot of birds might chose to use their regular forms. But they shouldn't be treated like second class patients!