Very few people seek dog training help with only one little problem. Typically there are a few things that need addressed, sometimes these are related and sometimes not. Here's the things we think about when trying to prioritize.
1) What are the safety risks? We need to minimize risk for the dog, the people, and any other animals. This means getting solid management plans in place and addressing the issue through a few different training angles. Example: Anything involving growling, freezing, snapping, unhappy barking, jumping up if there are small kids, etc.
2) Will one thing work towards solving multiple issues? In TAGTeach there's a thing called a "Value Added Tag" where one clickable moment will solve many different problems. There's no word for this in clicker training, but the same sort of thing exists. Example: A dog bites his owner....when the person is "punishing" the dog for eliminating indoors. Solution: Housetrain the dog dog..... no more accidents inside, no more biting. The dog still needs some handling training...but we're closer to success.
3) Which aspects cause the most stress in daily life? Tackle the bigger issues. Later, address the things that only come up in rare situations. It is all important and can all be addressed.... but save the smaller things for later.
4) Which aspects have the potential for great damage to the human-animal bond? Sometimes these are the same as question 3...but not always. Sometimes the people don't realize the bigger issues at hand or they don't realize how the issue could get worse if not addressed. Example: I walked into an appointment for a dog that is not social (but not afraid/aggressive) with people. I find the dog has torn up furniture all over the house after busting out of his crate that day. The people are worried that the dog is not actively social. I am worried about the destruction/separation distress.