In a experiment , a scientist should

They should ask a question, come up with a hypothesis then a testable explanation to address this question then do the experiment do the observations and see if they are right about their hypothesis

Explanation:

These are the things a scientist should do before going at it

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.