What questions are asked during the update or upgrade process? It would be good to know beforehand in case we choose the wrong option when asked and there is no turning back.
I don't know if you're talking about a normal upgrade, which you do about once a week - perhaps more often, or an upgrade from one major version to another, but the answer is the same for both:
There are some, rare, cases (in both upgrades and release-upgrades), where a service or a post-install script will ask something, examples for this are
There also can be cases where you need to decide whether to keep an old configuration file or replace it with a new one. You will be asked to either replace, keep or compare, in any case - if you didn't change a configuration file manually, it's normally safe to replace it with the new one.
If a question is asked of you, and you really don't know what to do, just hit enter (or
Ubuntu, with it's installer, tries hard to ask few questions only.
From my experience that works quite well;
There are two kinds of questions that are asked from time to time,
The questions can moastly be separated into two categories:
Configuration change conflicts:
Obviously, the second category requires much more attention than the first, but they are not very frequent. When I updated my Ubuntu 13.10 to 14.4, I had to handle maybe four of these, plus two more "obviously irrelevant" (that was for a system in less-than-perfect state of administration).
In terms of, referring to your question, "better being prepared": These conflicts are sometimes hard to resolve, ie if the "diff" is noisy, or the background of the manual change is not clear. But it is possible to keep both file variants as backup and resolve it manually later. (That could leave the configuration of an important service incomplete or broken, so do take a note.)