One of the quickest ways to learn about a research field is to talk to others working in the area. Trying to learn the fundamentals [key questions, techniques, background, …] by only reading can be a slow and inefficient process. Furthermore, key pieces of information, can be buried or not even there. So reading needs to be complemented by talking to others. They don't have to be the worlds leading expert.
Yet this is a very hard process and many students give up too easily. First, there is the problem of finding someone who both knows enough and will take the time to talk to you. Second, you will probably feel dumb. It requires courage and confidence to do this. You may not even know what questions to ask. Much of the jargon/language they use may be unfamiliar or meaningless. Third, it is just plain hard work and requires a sustained effort.
Theorists and experimentalists talking to each other presents a special set of challenges.
So does talking across disciplines (chemists and physicists, biologists and physicists, …)
Here are some basic questions to ask:
What are you working on?
Why is this important?
What are the key papers in the field? Why are they significant?
What is the "holy grail" of the field?
What "results" in the field do you think are dubious?
What is X? I don't understand. Can you explain it to me with a simple physical or chemical picture?
What are the limitations of this technique?
Could you explain that to me again?
Listen for concepts, names, pictures, graphs, equations, results, problems, …. that keep coming up.
Complement your discussions with reading. You will begin to know what to look for and certain things will start to stand out.
If I could have my time over I would have done a lot more talking to people.