As a veterinary officer the day to day activities revolve around animals. Some animals including farm animals and pets may need treatment, vaccinations, spaying, neutering etc. Of course if you are running your own practise there are administrative duties as well. Other things that a veterinarian has to do on a regular basis is keeping up with the new techniques, treatment methods that are continuously coming up.

 In answer to the second part of the question about diagnosing problems. The first thing  a vet does is to ask the owner all the details about their pet- and all the things which they have observed since the animal has been ill. Then he or she will examine the animal all over, taking the temperature, checking the heart, counting respiration rate etc etc. Depending on what he finds it may then be necessary to take some blood samples for blood tests- or maybe something a little more specific eg a skin scraping from an itchy dog or a urine sample from one with suspected diabetes. If the animal has a lameness problem or has suffered an accident, xrays may be used to look for breaks (fractures) of the bones. Ultrasound scans and x rays can also be used to help diagnose problems with internal organs such as the gut. Basically most of the tests which are used in human medicine are also used in animal medicine and your vet may be able to do many of them himself- although some of the equipment may only be available in specialist vet hospitals. I hope that answers your question, and is of interest to you.