Formulate your main claim
Claims should be concise, to the point and capable of being either supported or rejected. They should be expressed as statements or propositions, as in the following example:
Data mining of depersonalised health data poses a threat to privacy.
One way to formulate a claim is to begin with a question and then refine it:

Note that in order to formulate a claim, you need to make a decision. In our example, it means choosing between claim A (data mining poses a problem) and claim B (data mining does not pose a problem).
It is OK to be unsure of your claim when you first formulate it, or to change your mind when you bring together your reasons and evidence. Refining and improving is part of the process of developing an argument.