In Korean, there are only a handful of sentence patterns. Mastering these basic forms will provide the building blocks for everything else.
The basic form is simply:
Verb + Final Ending
(Note: You can use an adjective for the verb.)
You can add in a subject---the noun that is the actor.
Noun + 가 + Verb + Final Ending
Note that Koreans rarely, if ever, add the subject except when there is confusion. You should practice avoiding the use of the subject whenever possible. For instance, the statement "먹었다." means "I ate." because nothing else makes sense, unless you were being asked a question about whether someone else ate.
You can add the object in the sentence. This is the thing the subject is acting upon. Again, don't state it if it is obvious.
(Subject) noun+를 Verb+Final Ending
Although common, there are other postpositional phrases you can add as needed. If you know the following, you should know pretty much all of them:
Question final endings sometimes look exactly like the statement final endings. Sometimes the only way to distinguish is by intonation, because the question works (who? what? why? when? where?) can mean "someone", "something", "for some reason", "some time", "some place" respectively.
- 뭘 먹었어: "What did you eat?" or "Did you eat something?" or "I ate something."
Given the above, creating sentence clauses is actually quite simple. First, you put the statement together, then you add in the combining postposition, and that's all there is.
The above isn't the entire story. Koreans use several different common endings. You'll need to master them in order to communicate fluently.
Some people think that the various common endings represent entirely different sentence patterns. I do not. I think you're confusing yourself if you think that. Korean is far simpler than you expect it to be.
List of Common Sentence Patterns
I'm listing all the sentence patterns I know here.