Transforming your idea into a concise research question:
Determine what the broader topic of your idea is.
for example: if you're interested in the relation between school lunches and childhood obesity, the broader topic of that idea is "obesity," "childhood obesity," or "nutrition."
Do preliminary research on the broader topic(s) in order to find out what has already been said and done on that topic.
pay attention to what kind of studies have been done, and where articles/resources are regularly published.
After preliminary research, ask open-ended questions, like "why" or "how" to begin to narrow your research focus.
for example: if you've done preliminary research on childhood obesity, you may ask "how do we determine levels of childhood obesity," or even, "why is this an important issue to study?"
After answering the broader questions, begin to narrow your question and focus.
for example: if you're still interested in the relation between school lunches and childhood obesity, begin asking questions like, "what are the nutritional needs for children aged 5-10," or "what is the average nutritional value of a public school lunch in the United States?"
Narrowing your questions and finding the relevant answers to them should lead you to a specific research question as well as a possible argument with plenty of evidence to use for proof and counter arguments.
Your final research question may look something like this: "Are public school lunches a contributing factor to childhood obesity in the United States?" while your argument may be "No," provided you have relevant evidence from medical journals, nutritional data, and/or childhood development experts that support your argument.