Which one is correct in American English?
1) To prepare for something?
2) To get prepared for something?
Besides this, there are a lot of similar things that I am not sure about (such as to start or to get started). How can I generally realize which form is correct?
Both (1) and (2) are correct and commonly used forms and they mean almost exactly the same thing. The very subtle difference is that "to prepare" implies that the subject is actively to do the preparing while "to get prepared" could mean that the preparation is to be done for them.
Prepare is a verb. To prepare for something is to engage in the action of preparing.
Prepared is an adjective. It refers to being in a state of having completed preparations.
To prepare and to get prepared both refer to the same process, but with a slightly different nuance. To prepare focuses on the process of preparing, with no explicit attention to how long that will take. "We're preparing to send astronauts to Mars" is a true statement even if it is a minimal or sporadic effort occurring over decades.
To get prepared focuses on the end result. For preparation of a short duration, either phrase might be used. But it wouldn't be typical to select "to get prepared" when referring to a very long process that involved a lot of "biding time", or preliminary work to facilitate the task, like preparing to send astronauts to Mars.
Neither is wrong but in most cases To (verb) is preferable to To get (verbed).
Sometimes that means we need to prepare my/one/yourself and that’s a different question.
We should get going = we ought to be leaving
We should go = we ought to leave
The difference is that with get, the action is understood to be underway, to have commenced. That is, the action to be 'gotten' is one that is already underway.
Both sentences are correct.
If you were to ask a friend that you need to study for an exam coming up in a week, you would say...
"... and I need to get started on studying for English for the test this week."
Compare this to the alternative, this sounds much more realistic. This is how you'd distinct which one to use. To 'get' something done is implied that you want it done soon.
To prepare for the exam, Cuthbert spent many hours in quiet study.
To get prepared for the exam, Cathy drank a cup of cocoa and put on her extra strong reading glasses.
‘Prepare’ is more passive.
‘Get prepared’ (or get anything) focuses more on the action involved, and on the process, because ‘get’ describes the process of transitioning from not having - to having something.
Here’s another example:
He was drunk - describes his state. Nothing is happening - we just passively hear a description of how he now ‘is’. ie ‘drunk’. He is probably asleep on the staircase, key in hand.
He got drunk - is a whole other story - in fact it IS a story - it alludes to the process of how he got drunk. We might hear of several bars visited, various cocktails imbibed and bartenders met, in that ‘story’ of how he ‘got drunk’.
So neither is wrong - and the one you choose depends on whether you want to ‘describe the current status’ or ‘allude to the process’.
With start, or get started, the ‘get’ provides the impetus for the starting to happen - like a spark that ignites - again, it alludes to the process.
