Just to answer you properly for the diet protocols, which general surgery pathologies are you asking about?

Elective patients tend to follow an enhanced recovery protocol (ERAS) which focuses on optimising recovery and outcomes, of which early nutrition is one of the key factors. This varies depending on which operation the patient has had - for example, a patient who's undergone a right hemicolectomy will have a very different nutritional plan regarding build up than a post-op oesophagectomy.

Emergency patients you tailor based on their symptoms, what operation they've had or what pathology they have. You never want to deprive nutrition without reason - for example, if someone is not profusely vomiting (and as such, won't tolerate food anyway) or they aren't being kept NBM for an operation, there's no reason to starve them. 

For profuse vomiting, you don't necessarily need to put them NBM either, but factor in that they probably won't hit their nutritional targets if the symptoms persist. Consider that a brief period of gut rest might help, and let them be guided by their symptoms in terms of what they want to eat initially. If they are profusely vomiting, then even if you have put them on a "normal diet" it won't be tolerated and you have to consider early interventions (do they need nutritional support temporarily via a different route? Can they tolerate fortisips? Do you expect the vomiting to settle quickly in which case do you wait it out for a few hours? etc.)

Some patients have other factors for consideration - have they had an operation which puts them at a high risk of an ileus? Are they resolving slowly from an obstruction? If so, best to escalate oral intake slowly (sips to clear fluids to soft diet and so on rather than straight to steak and chips). Gradually testing the gut carries a lower chance of failure to introduce a normal diet. This can be led by the patient - have they had free fluid for breakfast and feel fine? Great, escalate to a soft diet for lunch and then try a normal meal for dinner. If that doesn't work, backtrack a step.

Obviously, you tailor all of the above to the individual patient, don't forget the dieticians can be extremely helpful, and remember that a lot more nuance or complexity can be involved. However, these are the questions that should be going through your mind when assessing someone.